According to E! Online, West rented out the Giants ballpark and proposed to Kardashian using the jumbo screen, which flashed "PLEEEASE MARRY MEEE!!!" A 50-piece orchestra was also on hand.
West reportedly gave Kardashian a 15-carat diamond ring.
After the proposal, West and Kardashian were joined by friends and family.
West is in the Bay Area as part of his Yeezus tour. He is performing at the SAP Center in San Jose Tuesday night.
Monday was Kardashian's 33rd birthday.
West and Kardashian have a daughter together, 4-month-old North West.