The incident happened around 1:45 p.m. Wednesday in the area near Deerfield and Yale avenues.
Police say the girl was walking along the street ahead of her siblings when she passed a suspect who called her over to his car. That's when she claims the suspect asked her where she went to school and where she lived.
While he was talking to her, he asked her if she had "seen this," and then exposed himself, Lt. Julia Engen of the Irvine Police Department said.
The victim claims she walked away and told family members what happened after arriving home.
The suspect, described as a man in his 30s, was last seen wearing an orange shirt, blue jeans, and driving a white vehicle.
Irvine police will increase patrols in the area when children are walking to and from school in response to the incident, Engen said.
CNS contributed to this report.