Northern elephant seals are found in the eastern and north central North Pacific. Breeding takes place on offshore islands and at a few mainland localities from central Baja California to Northern California. The species breeds at over fifteen discrete locations, of which a dozen are well-known and distributed mostly in islands of southern California (USA) and Baja California (Mexico) (Condit et al. in press). A few pups are born in Oregon, Washington and southern British Columbia. Año Nuevo, in Central California, is a major breeding site.

Northern elephant seals migrate to and from their rookeries twice a year, returning once to breed from December to March and again later for several weeks to molt, at different times depending on sex and age. They also show up at additional coastal sites as far north as southern Oregon for moulting. Their post-breeding and post-moult migrations take most seals north and west to oceanic areas of the North Pacific and Gulf of Alaska twice a year. Adult males tend to travel further north and west than adult females. Wanderers have been found as far away as Japan and the Midway Islands.