The company, WildWater Express Carwash, said malware was installed on its sales system.
The hackers were able to get access to customers' card numbers and pin codes.
The data breach impacts customers who used the car wash between Feb. 10 and 28.
WildWater Express Carwash has locations in San Pedro, Costa Mesa, Buena Park and Huntington Beach.
The company is offering one year of free credit monitoring through a third party. Impacted customers can visit http://activate.kroll.com or call 1-855-223-7528.