UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN ISSUER
PURSUANT TO RULE 13a-16 OR 15b-16 OF
THE SECURITIES EXCHANGE ACT OF 1934

For the month of December 2018

Commission File Number 001-35991

GRAÑA Y MONTERO S.A.A.

(Exact name of registrant as specified in its charter)

N/A

(Translation of registrant’s name into English)

Republic of Peru

(Jurisdiction of incorporation or organization)

Avenida Paseo de la República 4667, Lima 34,

Surquillo, Lima

Peru

(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.

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): [ ]

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): [ ]

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

If "Yes" is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): Not applicable.

We hereby inform as a Relevant Information Communication that today, within the framework of the investigations conducted in relation to the IIRSA South project (tranches II and III), The Peruvian First National Preparatory Investigation Court (Primer Juzgado de Investigación Preparatoria Nacional) declared founded the resolution incorporating as Civilly Responsible Third Party, among others, to Graña y Montero S.A.A. and GyM S.A. presented by the Procurator's Office several months ago, as it was made public by the press.

The Graña y Montero Group has been working closely with the State under the framework of Law 30737 to guarantee any obligation that could result from the aforementioned investigation, in case that at the end of the due process the company is charged with civil liability, and expects to conclude with the necessary agreements to make these guarantees effective at the end of January.

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.

By: /s/ LUIS FRANCISCO DIAZ OLIVERO
Name: Luis Francisco Diaz Olivero
Title: Chief Executive Officer
Date: December 18, 2018