The murderer was most likely robbing the restaurant overnight and killed 36-year-old Douglas Castello, an employee, with a blunt object to the head, according to the Police Department.
A daytime manager found the Hayward resident dead on the floor around 5:15 a.m. at the restaurant on 3101 S. El Camino Real on Jan. 19.
It was the first homicide in the city since April 2006.
Police Chief Susan Manheimer made a request to Schwarzenegger's office for the reward, indicating the Police Department pursued all possible leads and the money would help its efforts, according to the governor's office.
T.G.I. Friday's Inc. announced a $10,000 reward the same month as the homicide for information leading to an arrest and conviction.
The Governor's Reward Program started in 1967 and allows any law enforcement agency to request a reward for help in solving a case.