The attack happened on Butler and Chestnut near Fresno Pacific University in southeast Fresno.
Investigators say the victim was conscious and breathing, but he was rushed to the hospital with life-threatening injuries.
They say the attacker lived in the same home as the victim.
"It's my understanding this home is a mental health slash sober living residence. Our officers began to interview those residents and it appears there was some type of disturbance that happened between the suspect and the victim, which resulted in a stabbing," said Lt. Skye Leibee.
Investigators say the victim's attacker immediately ran off.
Neighbors were told to briefly shelter in place as K-9 units and a helicopter searched for the suspect.
Police haven't released a suspect description.