Police say Paul Corona, 52, of Caldwell, Idaho stabbed the male victim near Los Angeles Avenue and Grimes Canyon Road around 3:30 p.m.
They were allegedly fighting over a road rage incident involving two vehicles.
Corona was arrested for assault with a deadly weapon at the scene.
The stabbing victim was taken to the hospital where he underwent surgery for his stab wound.
Deputies from the Moorpark Patrol Station and officers from the California Highway Patrol are asking anyone who may have witnessed all or part of the fight or stabbing to come forward. Authorities are specifically looking for a woman in an older dark sedan which information indicates could be a key witness.
If you have any information regarding this incident, you're urged to contact the Ventura County Sheriff's office at (805) 654-2380.