The California Sea Lion occurs in the eastern North Pacific from Islas Tres Marias north of Puerto Vallarta, north throughout the Gulf of California and around the end of the Baja California Peninsula north to the Gulf of Alaska. Sightings of vagrants have been reported from the southern Bering Sea in the north (Maniscalco et al., 2004) to Chiapas Mexico in the south. Females, which were only very rarely found north of Point Conception in the early 1980s, are now routinely found in northern California, where former breeding sites have been reoccupied.

Large numbers of adult and subadult males and juveniles undertake a post-breeding season migration north from the major rookeries in southern California and Baja California and winter from central California to Washington State. Smaller numbers of animals migrate to British Columbia and southeast Alaska, making it to the northern Gulf of Alaska, Alaska Peninsula, and eastern Aleutian Islands. Other animals appear to remain in the Gulf of California year round and do not undertake long migrations.