The shooting happened shortly before 5 pm on McKinley and Fairfax.
Authorities arrived to find two victims suffering from gunshot wounds in their vehicle.
Detectives say they were shot at by a suspect or suspects in another vehicle heading in the same direction.
Both victims were rushed to hospital and one of them is in critical condition after being hit in the neck.
Authorities are talking to witnesses and searching for any home surveillance.
Fresno County Sheriff's detectives blocked off westbound McKinley Avenue between Cedar and Millbrook Avenues on Sunday evening as they carried out their investigation.
Anyone with information is asked to contact the Fresno County Sheriff's Office.