6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16 UNDER

THE SECURITIES EXCHANGE ACT OF 1934

For the month of March 2025

Commission File Number: 001-38638

NIO Inc.

(Registrant’s Name)

Building 19, No. 1355, Caobao Road, MinhangDistrictShanghai, People’s Republic of China

(Address of Principal Executive Offices)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F x       Form 40-F ¨

EXHIBIT INDEX

SIGNATURES

Pursuant to the requirements 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.

Date: March 11, 2025

Exhibit 99.1

HongKong Exchanges and Clearing Limited and The Stock Exchange of Hong Kong Limited take no responsibility for the contents of this announcement,make no representation as to its accuracy or completeness and expressly disclaim any liability whatsoever for any loss howsoever arisingfrom or in reliance upon the whole or any part of the contents of this announcement.

Underour weighted voting rights structure, our share capital comprises Class A ordinary shares and Class C ordinary shares. EachClass A ordinary share entitles the holder to exercise one vote, and each Class C ordinary share entitles the holder to exerciseeight votes, respectively, on any resolution tabled at our general meetings, except as may otherwise be required by law or by the Rules Governingthe Listing of Securities on The Stock Exchange of Hong Kong Limited or provided for in our memorandum and articles of association. Shareholdersand prospective investors should be aware of the potential risks of investing in a company with a weighted voting rights structure. OurAmerican depositary shares, each representing one of our Class A ordinary shares, are listed on the New York Stock Exchange in theUnited States under the symbol NIO.

NIO Inc.

(Acompany controlled through weighted voting rights and incorporated in the Cayman Islands with limited liability) (StockCode: 9866)

DATE OF BOARD MEETING

The board of directors (“Board”) of NIO Inc. (the “Company”) will hold a Board meeting on Friday, March 21, 2025 (Beijing/Hong Kong/Singapore Time) for the purposes of, among other things, approving the Company’s unaudited financial results for the three months and full year ended December 31, 2024 (“Q4 and FY2024 Results”). The Company will publish its Q4 and FY2024 Results on Friday, March 21, 2025 (Beijing/Hong Kong/Singapore Time) on the website of The Stock Exchange of Hong Kong Limited at www.hkexnews.hk and the website of the Company at ir.nio.com.

The Company’s management will host an earnings conference call at 8:00 p.m. Beijing/Hong Kong/Singapore Time on March 21, 2025 (8:00 a.m. U.S. Eastern Time on March 21, 2025).

A live and archived webcast of the conference call will be available on the Company’s investor relations website at https://ir.nio.com/news-events/events.

For participants who wish to join the conference using dial-in numbers, please register in advance using the link provided below and dial in 10 minutes prior to the call. Dial-in numbers, passcode and unique access PIN would be provided upon registering.

https://s1.c-conf.com/diamondpass/10045556-h7fg45.html

Hong Kong, March 11, 2025

As of the date of this announcement,the Board of the Company comprises Mr. Bin Li as the chairman, Mr. Lihong Qin, Mr. Eddy Georges Skaf and Mr. NicholasPaul Collins as the directors, and Mr. Hai Wu, Mr. Denny Ting Bun Lee, Ms. Yu Long and Mr. Yonggang Wen as the independentdirectors.