Nearly 200 inmates at San Quentin State Prison rioted in the dining hall, leaving four men injured with stab or slash wounds.
Three of the inmates injured in the Sunday night incident returned to the prison after receiving treatment, while one remained hospitalized.
Guards stopped the brawl using non-lethal bullets and pepper spray, and found at least 10 weapons made by inmates, prison spokesman Lt. Samuel Robinson said.
The cause of the riot was under investigation.
Robinson said authorities don't know if it was connected to another serious melee at California State Prison, Sacramento on Friday. That riot involved 150 inmates and resulted in six injuries, including two considered serious.
No guards were hurt in either riot.
San Quentin is located in Marin County, north of San Francisco. It's the state's oldest prison and houses nearly 5,000 men, including those on death row.
Meanwhile, the U.S. Supreme Court on Monday narrowly endorsed reducing California's cramped prison population by more than 30,000 inmates to fix sometimes deadly problems in medical care, ruling that federal judges retain enormous power to oversee troubled state prisons.
The court said in a 5-4 decision the reduction is required by the Constitution to correct longstanding violations of inmates' rights. The order mandates a prison population of no more than 110,000 inmates, still far above the system's designed capacity.