|        |
|--------|
|        |  |
| ý | Quarterly Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 |

|        |
|--------|
|        |  |
| ¨ | Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 |

|                                             |
|---------------------------------------------|
|                                             |  |  |
| Delaware                                    |   | 34-0244000 |
| (State of Incorporation)                    |   | (I.R.S. EmployerIdentification No.) |
|                                        |   |
| 2001 Aerojet RoadRancho Cordova, California |   | 95742 |
| (Address of Principal Executive Offices)    |   | (Zip Code) |
|                                        |   |
| P.O. Box 537012Sacramento, California       |   | 95853-7012 |
| (Mailing Address)                           |   | (Zip Code) |

|                                   |
|-----------------------------------|
|                                   |  |  |  |  |
| Large accelerated filer | ý | Accelerated filer |   | ¨ |
|                              |   |   |   |
| Non-accelerated filer             | ¨ (Do not check if a smaller reporting company) | Smaller reporting company |   | ¨ |

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|                  |
|------------------|
|                  |  |  |
| No.              |    | Description |
|             |   |
| 31.1*            |    | Certification of Principal Executive Officer pursuant to Rule 13a — 14 (a) of the Securities Exchange Act of 1934, as amended. |
| 31.2*            |    | Certification of Principal Financial Officer pursuant to Rule 13a — 14 (a) of the Securities Exchange Act of 1934, as amended. |
| 32.1*            |    | Certification of Principal Executive Officer and Principal Financial Officer pursuant to Rule 13a — 14(b) of the Securities and Exchange Act of 1934, as amended, and 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. |
|   101* |    | The following materials from the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2016, formatted in XBRL (Extensible Business Reporting Language): (i) Unaudited Condensed Consolidated Statements of Operations, (ii) Unaudited Condensed Consolidated Statements of Comprehensive Income, (iii) Unaudited Condensed Consolidated Balance Sheets, (iv) Unaudited Condensed Consolidated Statement of Stockholders’ Deficit, (v) Unaudited Condensed Consolidated Statements of Cash Flows, and (vi) Unaudited Notes to Unaudited Condensed Consolidated Financial Statements, as filed on May 10, 2016. |

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|        |
|--------|
|        |  |  |  |  |
|   |   |   |   |   |
|   |   | Aerojet Rocketdyne Holdings, Inc. |
|   |   |   |   |
| Date:  | August 16, 2016 | By: |   | /s/ Eileen P. Drake |
|   |   |   |   | Eileen P. DrakePresident and Chief Executive Officer(Principal Executive Officer) |
|   |   |   |   |
| Date:  | August 16, 2016 | By: |   | /s/ Kathleen E. Redd |
|   |   |   |   | Kathleen E. Redd                                    Vice President, Chief Financial Officer and Assistant Secretary (Principal Financial Officer andPrincipal Accounting Officer) |

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|                  |
|------------------|
|                  |  |  |
| No.              |    | Description |
|             |   |
| 31.1*            |    | Certification of Principal Executive Officer pursuant to Rule 13a — 14 (a) of the Securities Exchange Act of 1934, as amended. |
| 31.2*            |    | Certification of Principal Financial Officer pursuant to Rule 13a — 14 (a) of the Securities Exchange Act of 1934, as amended. |
| 32.1*            |    | Certification of Principal Executive Officer and Principal Financial Officer pursuant to Rule 13a — 14(b) of the Securities and Exchange Act of 1934, as amended, and 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. |
|   101* |    | The following materials from the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2016, formatted in XBRL (Extensible Business Reporting Language): (i) Unaudited Condensed Consolidated Statements of Operations, (ii) Unaudited Condensed Consolidated Statements of Comprehensive Income, (iii) Unaudited Condensed Consolidated Balance Sheets, (iv) Unaudited Condensed Consolidated Statement of Stockholders’ Deficit, (v) Unaudited Condensed Consolidated Statements of Cash Flows, and (vi) Unaudited Notes to Unaudited Condensed Consolidated Financial Statements, as filed on May 10, 2016. |