(800) 375-5283The USCIS California Service Center, operating under the Department of Homeland Security, is tasked with processing immigration and naturalization-related forms. Staff members are available for assistance from Monday to Friday, between the hours of 8:00 a.m. and 4:00 p.m., with closure on Saturday and Sunday. Petitioners must contact the staff during these working hours. The staff at the USCIS California Service Center carries out crucial duties, such as processing applications for work visas, asylum, naturalization, green cards, refugee status, and adjudicating petitions. USCIS is responsible for safeguarding national security.