The shooting occurred about 11:30 p.m. as the woman was taking a shower at their residence in a mobile home park in the 6700 block of Lincoln Avenue, near Knott Avenue, a spokesperson for the Buena Park Police Department.
While cleaning the firearm, the man was loading it back when the gun discharged and a round struck his wife in the shoulder, police said.
The wounded woman was transported to a hospital where she was listed in stable condition.
The gun was confiscated and no arrest was made, the police spokesperson said.
The incident is being investigated as a negligent discharge, according to authorities.