The major crash happened at 14700 North Freeway, on the northbound service road near Airtex Drive.
Deputies said both the adult and the child were deceased when they arrived on scene.
Sheriff Ed Gonzalez said the man who died appeared to be in his 20s, and the child is between the ages of eight and 10 years old.
He also said a second car was involved and that those occupants have been transported to the hospital. Their condition is unknown.
The northbound service road and westbound lanes of Airtex Drive are currently shut down.