St John spokesman Robbie Walker confirmed one person had suffered serious injuries. An ambulance was called to Eden Park by event staff about 7.40pm.
The person was treated at the scene with serious injuries and then transported to Auckland City Hospital.
A bumper Eden Park crowd of more than 48,000 saw the All Blacks smash the Wallabies 51-20 to retain the Bledisloe Cup.
Meanwhile, power was cut to about 900 unlucky homes in Mt Eden during the game.
The outage hit about 8pm after a transformer on Sandringham Rd lost power, but Eden Park was not affected.
Vector spokeswoman Sandy Hodge said crews were unclear what caused the outage.
Power was restored to all but 288 homes about 30 minutes later and was expected to be fully restored by 9.30pm.