Court documents show Harris, 30, became angry when Geier attempted to put soy sauce on Harris' rice at Su Hung restaurant in Menlo Park in August 2012.
Harris then accused Geier of stealing his underwear, County Prosecutor Al Serrato said, and tried to pull down Geier's pants, before pinning Geier against a glass window and hitting him several times in the face and head.
"We're disappointed, but we're obviously relieved they acquitted him of the felonies," said Harris' attorney, Alin Cintean, adding he plans to appeal the verdict.
Harris, who is to be sentenced Nov. 12, played for the 49ers for five years before signing with the Raiders as a free agent. He was released in 2008.