Neighbors first reported a sea lion was hiding under a car at Marina Boulevard and Divisadero Street shortly after 6:30 a.m.
Police officers assisted in keeping the animal out of harm's way until animal rescuers from the Marine Mammal Center arrived.
About 30 minutes later, the sea lion was rescued, put in a carrier and taken back to the Marine Mammal Center for assessment.
The male California sea lion, nicknamed Rubbish, had received treatment for pneumonia at the center after being found malnourished by the Santa Barbara Marine Mammal Center in February. He was released on March 23 after gaining 17 pounds.
But five weeks later, he lost all the gained weight. Marine Mammal Center officials will hold on to Rubbish for some time to run tests.
Thousands of California sea lion pups have stranded along the California coast this year as a result of warm waters that have affected food availability.