UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549





FORM 10-K/A





(Mark One)

|☒ | ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
|- | ------------------------------------------------------------------------------------

For the fiscal year ended December 31, 2017

or



|☐ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
|- | ----------------------------------------------------------------------------------------

For the transition period from
 to

Commission file number 001-37780





Randolph
Bancorp, Inc.

(Exact name of registrant as specified in its charter)







|                                                            |  |                                    
|----------------------------------------------------------- |  | -----------------------------------
|Massachusetts                                               |  | 81-1844402                         
|State or other jurisdiction ofincorporation or organization |  | (I.R.S. EmployerIdentification No.)



|                                         |  |           
|---------------------------------------- |  | ----------
|10 Cabot Place, Stoughton, MA            |  | 02072     
|(Address of principal executive offices) |  | (Zip Code)

(781) 963-2100

Registrants telephone number, including area code

Securities registered pursuant to Section 12(b) of the Act:



|                                       |  |                                          
|-------------------------------------- |  | -----------------------------------------
|Title of each
class                    |  | Name of each exchange on
which registered
|Common Stock, par value $.01 per share |  | NASDAQ                                   

Securities registered pursuant to section 12(g) of the Act:

(Title of class)

(Title
of class)





Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities
Act.  ☐ Yes ☒  No

Indicate by check mark if the registrant is not required to file reports
pursuant to Section 13 or Section 15(d) of the Act.  ☐ Yes ☒  No

Indicate by check
mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file
such reports), and (2) has been subject to such filing requirements for the past 90 days.  ☒ Yes ☐  No

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data
File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such
files).  ☒ Yes ☐  No

Indicate by check mark whether the registrant is a large accelerated filer,
an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of large accelerated filer, accelerated filer and smaller reporting company and emerging growth
company in Rule 12b-2 of the Exchange Act.



|                        |  |                                                  |  |                           |  |  
|----------------------- |  | ------------------------------------------------ |  | ------------------------- |  | -
|Large accelerated filer |  | ☐                                                |  | Accelerated filer         |  | ☒
|                        |  |                                                  | 
|Non-accelerated filer   |  | ☐  (Do not check if a smaller reporting company) |  | Smaller reporting company |  | ☐
|                        |  |                                                  | 
|                        |  |                                                  |  | Emerging growth company   |  | ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended
transition period for complying with any new or revised financial account standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§ 229.405 of this chapter) is not
contained herein, and will not be contained, to the best of registrants knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form
10-K.  ☐ Yes ☒  No

Indicate by check mark whether the registrant is a shell company (as defined
in Rule 12b-2 of the Act).  ☐ Yes ☒  No

The aggregate market value of the voting and non-voting
common equity held by non-affiliates as of the last business day of the registrants most recently completed second fiscal quarter was $78,736,498.

Indicate the number of shares outstanding of each of the registrants classes of common stock, as of the latest practicable date:
6,029,776 shares as of March 15, 2018.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the Registrants Proxy Statement for its 2018 Annual Meeting of Shareholders are incorporated by reference into Part III of
this Form 10-K.









---

Explanatory Note

This Amendment No. 1 to the Annual Report on Form 10-K (this Amendment) amends the Annual Report on Form 10-K for the fiscal
year ended December 31, 2017, originally filed with the Securities and Exchange Commission (the SEC) on March 16, 2018 (the Form 10-K), by Randolph Bancorp, Inc. (the Company). The sole purpose of this
Amendment is to correct the Report of Independent Registered Public Accounting Firm which had incorrectly stated that Crowe Horwath LLP had served as the Companys auditor since 2013. Crowe Horwath LLP has served as the
Companys auditor since 2015.

In addition, as required by Rule 12b-15 under the Securities Exchange Act of 1934, as amended, new
certifications by the Companys principal executive officer and principal financial officer are filed as exhibits to this Amendment.

No changes have been made in this Amendment to modify or update the other disclosures presented in the Form 10-K. This Amendment does not
reflect events occurring after the filing of the Form 10-K or modify or update those disclosures that may be affected by subsequent events. This Amendment should be read in conjunction with the Form 10-K and the Companys other filings made
with the SEC.



---

Item 8. Financial Statements and Supplementary Data.

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Shareholders and the Board of Directors of

Randolph Bancorp,
Inc.

Stoughton, Massachusetts

Opinion on the Financial
Statements

We have audited the accompanying consolidated balance sheets of Randolph Bancorp, Inc. (the Company) as of December 31,
2017 and 2016, the related consolidated statements of operations, comprehensive loss, changes in stockholders equity, and cash flows for the years then ended, and the related notes (collectively referred to as the financial
statements). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2017 and 2016, and the results of its operations and its cash flows for each of the
years then ended, in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements are the responsibility of the Companys management. Our responsibility is to express an opinion on the Companys financial
statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the
U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in
accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The
Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting in accordance with the standards of the PCAOB. As part of our audits we are required to obtain an understanding of internal
control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Companys internal control over financial reporting. Accordingly, we express no such opinion in accordance with the standards of the
PCAOB.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud,
and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles
used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

We have served as the Companys auditor since 2015.

/s/
Crowe Horwath LLP

New York, New York

March 15, 2018



---

Item 15. Exhibits, Financial Statement Schedules.

3. Exhibits:

Exhibit Index



|      |  |                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|----- |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|      | 
|2.1   |  | Agreement and Plan of Merger, dated as of September 
1, 2015, by and among Randolph Bancorp, First Eastern Bankshares Corporation and Richard F. Kalagher(1)                                                                                                                                                                                                                                                                                               
|      | 
|2.2   |  | Amendment No. 1 to Agreement and Plan of Merger, dated as of September 15, 2015, by and among Randolph Bancorp, First Eastern Bankshares Corporation
 and Richard F. Kalagher(1)                                                                                                                                                                                                                                                                           
|      | 
|2.3   |  | Amendment No. 2 to Agreement and Plan of Merger, dated as of February 5, 2016, by and among Randolph Bancorp, First Eastern Bankshares Corporation
 and Richard F. Kalagher(1)                                                                                                                                                                                                                                                                             
|      | 
|3.1   |  | Articles of Organization of Randolph Bancorp, Inc.(1)                                                                                                                                                                                                                                                                                                                                                                                                      
|      | 
|3.2   |  | By-Laws of Randolph Bancorp, Inc.(1)                                                                                                                                                                                                                                                                                                                                                                                                                       
|      | 
|4.1   |  | Form of Common Stock Certificate of Randolph Bancorp, Inc.(1)                                                                                                                                                                                                                                                                                                                                                                                              
|      | 
|10.1 |  | Randolph Savings Bank Supplemental Retirement Plan(1)                                                                                                                                                                                                                                                                                                                                                                                                      
|      | 
|10.2 |  | Form of Randolph Savings Bank Employee Stock Ownership Plan(1)                                                                                                                                                                                                                                                                                                                                                                                             
|      | 
|10.3 |  | Employment Letter, dated as of March 22, 2013, by and between Randolph Savings Bank and James P. McDonough(1)                                                                                                                                                                                                                                                                                                                                              
|      | 
|10.4 |  | Letter Amending Employment Letter, dated as of June 30, 2016, by and between Randolph Savings Bank and James P. McDonough(2)                                                                                                                                                                                                                                                                                                                               
|      | 
|10.5 |  | Form of Change in Control Agreement(1)                                                                                                                                                                                                                                                                                                                                                                                                                     
|      | 
|10.6  |  | Randolph Bancorp, Inc. 2017 Stock Option and Incentive Plan(3)                                                                                                                                                                                                                                                                                                                                                                                             
|      | 
|14.1  |  | Code of Business Conduct and Ethics(4)                                                                                                                                                                                                                                                                                                                                                                                                                     
|      | 
|21.1  |  | Subsidiaries of the Registrant(5)                                                                                                                                                                                                                                                                                                                                                                                                                          
|      | 
|23    |  | Consent of Independent Registered Public Accounting Firm                                                                                                                                                                                                                                                                                                                                                                                                   
|      | 
|31.1  |  | Certification of Chief Executive Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002                                                                                                                                                                                                                                                                                                                                                         
|      | 
|31.2  |  | Certification of Chief Financial Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002                                                                                                                                                                                                                                                                                                                                                         
|      | 
|32.1* |  | Certifications of Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002                                                                                                                                                                                                                                                                             
|      | 
|101   |  | The following financial statements for the years ended December 31, 2017 and 2016, formatted in XBRL (Extensible Business Reporting Language): (i) Consolidated Balance Sheets, (ii) Consolidated Statements of Operations, (iii)
Consolidated Statements of Comprehensive Loss, (iv) Consolidated Statements of Changes in Stockholders Equity, (v) Consolidated Statements of Cash Flows and (vi) the Notes to the Consolidated Financial Statements.(5)



|(1) | Incorporated by reference to the Registration Statement on Form S-1 (File No. 333-209935), originally filed with the SEC on March 4, 2016.
|--- | ------------------------------------------------------------------------------------------------------------------------------------------

|(2) | Incorporated by reference to the Registrants Current Report on Form 8-K filed on July 6, 2016.
|--- | -----------------------------------------------------------------------------------------------

|(3) | Incorporated by reference to the Registrants Current Report on the Form 8-K filed with the SEC on August 23, 2017.
|--- | -------------------------------------------------------------------------------------------------------------------

|(4) | Incorporated by reference to the Registrants Annual Report on Form 10-K for the year ended December 31, 2016 as filed with the SEC on March 28, 2017.
|--- | ------------------------------------------------------------------------------------------------------------------------------------------------------

|(5) | Incorporated by reference to the Registrants Annual Report on Form 10-K for the year ended December 31, 2017 as filed with the SEC on March 16, 2018.
|--- | ------------------------------------------------------------------------------------------------------------------------------------------------------

| | Management contract or compensation plan or arrangement
|- | -------------------------------------------------------

|* | These certifications are not filed for purposes of Section 18 of the Exchange Act or incorporated by reference into any filing under the Securities Act or the Exchange Act.
|- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|(b) | See (a)(3) above for all exhibits filed herewith and the Exhibit Index.
|--- | -----------------------------------------------------------------------

|(c) | Financial Statement Schedules. None.
|--- | ------------------------------------



---

Signatures

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized.



|                    |  |  |  |    |  |                                                               
|------------------- |  |  |  | -- |  | --------------------------------------------------------------
|                    |  |  |  |    |  | RANDOLPH BANCORP, INC.
(Registrant)                           
|                    |  |  | 
|Date: April 6, 2018 |  |  |  | By |  | /s/ James P. McDonough                                        
|                    |  |  |  |    |  | James P. McDonough                                            
|                    |  |  |  |    |  | Director, President, and Chief Executive Officer              
|                    |  |  |  |    |  | (principal executive officer)                                 
|                    |  |  | 
|Date: April 6, 2018 |  |  |  | By |  | /s/ Michael K. Devlin                                         
|                    |  |  |  |    |  | Michael K. Devlin                                             
|                    |  |  |  |    |  | Executive Vice President and Chief Financial Officer          
|                    |  |  |  |    |  | (principal financial officer and principal accounting officer)