Emergency services were called to a report of an unexplained death in Matipo St, Riccarton about 3.50am on Tuesday.
“Inquiries are ongoing to determine the circumstances of the incident,” a police spokesperson said.
The Herald understands the man who died was a university student.
The University of Canterbury has been approached for comment.

The homeowner told the Herald he was aware there was an incident at the rental property, but declined to comment further.
The police cordon is outside Wharenui School, near Blenheim Rd, beside Wharenui Swimming Pool and Sports Centre.

Five red and yellow soft jump packs can be seen open with masks, gloves and bandages at the intersection near traffic lights and on the footpath.
A police forensics tent has now moved to cover the section of road where the medical equipment and splatter of blood lies.
Police staff are now at work inspecting the scene.
Wharenui School has told parents that the school is open despite the cordons being in place.
“Unfortunately there has been an incident overnight in Riccarton on the corner of Elizabeth and Matipo Streets (on the opposite side of the road to the pool). Please be prepared to come into school from Rex Street or Blenheim Road end.”
A mobile police station has now arrived on Matipo St, at the same time as the school busses set to take students of neighbouring Wharenui School to their school camp.
Members of the public are asked to avoid the area.
By Sam Sherwood and Nathan Morton