UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED

PURSUANT TO 13d-2(b)

(Amendment No.     ) *

Qunar Cayman Islands Limited

(Name of Issuer)

Class B Ordinary Shares, par value $0.001 per share

(Title of Class of Securities)

74906P104

(CUSIP Number)

December 31, 2013

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

¨ Rule 13d-1(b)

¨ Rule 13d-1(c)

x Rule 13d-1(d)

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Qunar Cayman Islands Limited

17th Floor, Viva Plaza, Building 18, Yard 29,

Suzhou Street, Haidian District

Beijing 100080

The People’s Republic of China

Mayfield XII Management, L.L.C. (“MF XII Management”)

Mayfield XII, a Delaware Limited Partnership (“MF XII”)

Mayfield Associates Fund XII, a Delaware Limited Partnership (“MF AF XII”)

Mayfield Principals Fund XII, a Delaware Multiple Series LLC (“MF PF XII”)

James T. Beck

Navin Chaddha

Robert T. Vasan

c/o Mayfield Fund

2484 Sand Hill Road

Menlo Park, CA 94025

MF XII Management is a Delaware limited liability company

MF XII is a Delaware limited partnership

MF AF XII is a Delaware limited partnership

MF PF XII is a Delaware multiple series limited liability company

The individuals listed in Item 2(a) are U.S. citizens.

Class B ordinary shares, par value $0.001 (the “Class B shares”)

74906P104

Not applicable

The information regarding ownership as set forth in Items 5-9 of the cover pages hereto is hereby incorporated by reference

MF XII beneficially owns 13,841,864 Class B shares that are issuable upon the conversion of 13,841,864 Class A ordinary shares, which MF XII holds directly.

MF AF XII beneficially owns 214,045 Class B shares that are issuable upon the conversion of 214,045 Class A ordinary shares, which MF AF XII holds directly.

MF PF XII beneficially owns 214,045 Class B shares that are issuable upon the conversion of 214,045 Class A ordinary shares, which MF PF XII holds directly.

MF XII Management is the sole general partner of each of MF XII and MF AF XII and the sole Managing Director of MF PF XII, and in such capacity may be deemed to beneficially own the Class B ordinary shares beneficially held by each of MF XII, MF AF XII and MF PF XII. MF XII Management is managed by three managing directors, James T. Beck, Navin Chaddha and Robert T. Vasan, and all action by the managing directors relating to the voting or disposition of shares of Class B ordinary shares beneficially held by each of MF AF XII, MF PF XII and MF XII requires approval of a majority of the managing directors.

The managing directors of MF XII Management may be deemed to share beneficial ownership of the Class B ordinary shares that are beneficially owned by MF XII Management, but each disclaims such beneficial ownership.

See Item 11 of each cover page.

On a fully-diluted basis, MF XII Management beneficially owns 4.2% of the Class B shares, based on 39,332,950 Class B shares outstanding as of November 19, 2013, as reported on the Issuer’s report on Form 6-K filed November 21, 2013, and assuming that all of the 302,850,254 outstanding Class A ordinary shares are converted into an additional 302,850,254 Class B shares.

See Item 6 of each cover page.

See Item 8 of each cover page.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following  ¨.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: January 30, 2014

EXHIBIT INDEX

Exhibit 24.1

POWER OF ATTORNEY

Know all by these presents, that the undersigned hereby authorizes James T. Beck, for so long as he is an employee, member or partner of Mayfield, to execute for and on behalf of the undersigned, in the undersigned’s individual capacity, in the undersigned’s capacity as a member of any limited liability company and in the undersigned’s capacity as a partner of any general or limited partnership, (i) any and all filings pursuant to Section 16 of the Securities Exchange Act of 1934 (the “Exchange Act”), including any and all Forms 3, 4 and 5, and Section 13 of the Exchange Act, including Schedules 13D and 13G, and any amendments thereto and joint filing agreements and other documents in connection therewith, and (ii) any applications for EDGAR access codes, including the Form ID, in each case as may be required to be filed from time to time with the U. S. Securities and Exchange Commission with respect to any investments of Mayfield Fund and its affiliates (collectively, “Mayfield”), and cause any and all of such forms, schedules, agreements and documents to be filed with the U. S. Securities and Exchange Commission pursuant to Section 13 and Section 16 of the Exchange Act, relating to the undersigned’s direct or indirect beneficial ownership of securities (in the undersigned’s individual capacity, or in the undersigned’s capacity as a member of any limited liability company or partner in any general or limited partnership). The undersigned hereby grants to such attorney-in-fact full power and authority

to do and perform any and every act and thing whatsoever requisite, necessary or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present, with full power of substitution or revocation, hereby ratifying and confirming all that such attorney-in-fact, or such attorney-in-fact substitute or substitutes, shall

lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted. The undersigned acknowledges that the foregoing attorney-in-fact, in serving in such capacity at the request of the undersigned, is not assuming, nor is Mayfield assuming, any of the undersigned’s responsibilities to comply with Section 16 or Section 13 of the Exchange Act.

This Power of Attorney shall remain in full force and effect until the undersigned is no longer an employee, member or partner of Mayfield, unless earlier revoked by the undersigned in a signed writing delivered to the foregoing attorney-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of this 31st day of January, 2011.

   /s/  Navin Chaddha

Exhibit 24.2

POWER OF ATTORNEY

Know all by these presents, that the undersigned hereby authorizes James T. Beck, for so long as he is an employee, member or partner of Mayfield, to execute for and on behalf of the undersigned, in the undersigned’s individual capacity, in the undersigned’s capacity as a member of any limited liability company and in the undersigned’s capacity as a partner of any general or limited partnership, (i) any and all filings pursuant to Section 16 of the Securities Exchange Act of 1934 (the “Exchange Act”), including any and all Forms 3, 4 and 5, and Section 13 of the Exchange Act, including Schedules 13D and 13G, and any amendments thereto and joint filing agreements and other documents in connection therewith, and (ii) any applications for EDGAR access codes, including the Form ID, in each case as may be required to be filed from time to time with the U. S. Securities and Exchange Commission with respect to any investments of Mayfield Fund and its affiliates (collectively, “Mayfield”), and cause any and all of such forms, schedules, agreements and documents to be filed with the U. S. Securities and Exchange Commission pursuant to Section 13 and Section 16 of the Exchange Act, relating to the undersigned’s direct or indirect beneficial ownership of securities (in the undersigned’s individual capacity, or in the undersigned’s capacity as a member of any limited liability company or partner in any general or limited partnership). The undersigned hereby grants to such attorney-in-fact full power and authority to do and perform any and every act and thing whatsoever requisite, necessary or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present, with full power of substitution or revocation, hereby ratifying and confirming all that such attorney-in-fact, or such attorney-in-fact substitute or substitutes, shall

lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted. The undersigned acknowledges that the foregoing attorney-in-fact, in serving in such capacity at the request of the undersigned, is not assuming, nor is Mayfield assuming, any of the undersigned’s responsibilities to comply with Section 16 or Section 13 of the Exchange Act.

This Power of Attorney shall remain in full force and effect until the undersigned is no longer an employee, member or partner of Mayfield, unless earlier revoked by the undersigned in a signed writing delivered to the foregoing attorney-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of this 31st day of January, 2011.

  /s/  Robert T. Vasan

Exhibit 99.1

JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1)(iii) promulgated under the Securities Exchange Act of 1934, as amended, we the undersigned agree that the Schedule 13G, to which this Joint Filing Agreement is attached as an Exhibit, including all amendments thereto filed by the undersigned, is filed on behalf of each of us.

Date: January 30, 2014