The incident occurred after the final bell rang at 3.20pm near Brightside Rd, Owens Rd and Gillies Ave.
Senior students escorted the youngster home after she ran away from the man, the school said.
The man was of Indian ethnicity, with spiky hair, about 20 years of age in a blue sedan with the letter H as the first letter on the number plate, the school said.
"We have notified our local schools and all of our girls and discussed strategies to keep safe -- walk in groups, always look out for especially the younger girls and don't hesitate to use iPhones to take photographs or call 111," the school said.
It was not providing further comment on the incident.
Detective Senior Sergeant Paul Newman said the incidents were being investigated.
"Police are aware of two reported incidents involving Diocesan pupils who have advised they were approached by an unknown man," he said.
The first reported incident occurred on Mauranui Ave about 4.30pm on Friday. A parent notified police shortly after 12pm yesterday, police said.
"Inquiries are being carried out into both reports," Mr Newman said.
"Police want to hear from anyone who saw any suspicious behaviour involving a dark-skinned man in a mid to dark blue vehicle, possibly a sedan, in or around either of these locations over the past week."
