Until recently, sergeants-at-arms, who are trained as law enforcement officers, were armed only when threat levels were high or during large events.
They will now be armed with .40-caliber semiautomatic handguns whenever they are on duty.
The Senate does not plan to implement the same policy.
Sergeants-at-arms in both chambers provide security for lawmakers and during committee meetings and floor sessions.
The California Highway Patrol also guards the Capitol.
The Associated Press contributed to this report.