Joanne Chatfield (17), went missing in central Auckland on 19 November 1988.
She was last seen leaving an event at Auckland University about midnight.
Joanne was likely the victim of foul play and despite the case remaining unsolved, police are determined to leave no stone unturned to confirm her fate and finally bring closure to her family, Detective Senior Sergeant Shaun Vickers said in a statement.
Accomplices who provide information or evidence leading to a conviction may receive immunity if they're not the main offender, police said.
Police have also renewed a $50,000 reward for material information or evidence leading to a conviction.
They say loyalties can change over time and they hope someone will come forward for Joanne and her family.
