Valeri came into the game for Kalif Alhassan to begin the second half with the Timbers trailing 1-0 and scored 5 minutes later on a volley past goalkeeper Dan Kennedy.
Portland (10-5-13), which holds fifth place in the Western Conference, notched its first road point since July 20.
Bryan de la Fuente scored for Chivas USA (6-15-8).
Notable deaths of 2014 [PHOTOS]
Julius Randle breaks leg during NBA debut