Police say the incident happened sometime after 10 p.m.
Officials with the Los Angeles County Fire Department say they responded with a helicopter to transport the victim to a hospital, where he was listed in fair condition and being treated for non-life threatening wounds.
Three people were detained, but it's unclear if they will be booked.
The cause of the fight was not known.
Leslie Galerne, a spokeswoman for the L.A. County Fair, issued a statement.
"We can confirm that there has been an incident at the L.A. County Fair tonight involving an individual injured in what appears to be a possible stabbing," Galerne said. "The individual sustained minor injuries and was alert and conscious before being transported as a precautionary measure to County U.S.C."