Company: AWK
Filing Date: 2025-03-21
Form Type: 11-K
Source: 0001410636-25-000065
Chunk: 0

Company: American Water Works Company, Inc.
Filing Date: 2025-03-21
Form: 11-K
Chunk 0
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### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### FORM 11-K
(Mark One)

| x |     | ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

#### For the fiscal year ended December 31, 2024
<div align='center'>OR</div>

| ¨ |     | TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

#### For the transition period

#### to

#### Commission File Number: 001-34028
A. Full title of the plan and the address of the plan, if different from that of the issuer named below:

<div align='center'>American Water Works Company, Inc. and its Designated Subsidiaries</div>

#### 2017 Nonqualified Employee Stock Purchase Plan
B. Name of issuer of the securities held pursuant to the plan and the address of its principal executive office:

#### American Water Works Company, Inc.

#### 1 Water Street

#### Camden, NJ 08102-1658

### TABLE OF CONTENTS
|                                                                                                         |     | Page |
| Report of Independent Registered Public Accounting Firm                                                 |     |    3 |
| Financial Statements                                                                                    |     |      |
| Statements of Financial Condition as of December 31, 2024and 2023                                       |     |    4 |
| Statements of Changes in Net Income and Plan Equity for the years ended December 31, 2024, 2023and 2022 |     |    5 |
| Notes to the Financial Statements                                                                       |     |    6 |
| Exhibit Index                                                                                           |     |    8 |
| Signatures                                                                                              |     |    9 |

<div align='center'>Report of Independent Registered Public Accounting Firm</div>

To the Benefit Administration Committee of

American Water Works Company, Inc.

#### Opinion on the Financial Statements
We have audited the accompanying statements of financial condition of American Water Works Company, Inc. and its Designated Subsidiaries 2017 Nonqualified Employee Stock Purchase Plan (the “Plan”) as of December 31, 2024 and 2023, and the related statements of changes in net income and plan equity for the years ended December 31, 2024, 2023, and 2022, and the related notes (collect