Police responded at E Street and Mariposa just after 4:30 am Friday.
They found the victim, an unhoused man in his 40's, bleeding on the sidewalk.
He had several injuries to his head and upper body, and was taken to the hospital.
Police haven't said what led up to the attack, or if they have any information on a suspect at this time.
Detectives are combing the area for evidence and interviewing any possible witnesses.