Four people were arrested on the first day of the Wellington Sevens rugby tournament and eight were thrown out of Westpac stadium.
Wellington Free Ambulance said 53 people needed treatment for intoxication, compared with about 80 last year.
The event is being attended by 31,432 spectators.
Fans over the age of 18 are required to wear wristbands inside the stadium and risk having their wristbands removed if they are intoxicated.
Inspector Terry Van Dillen said this new system has so far been a success.
Forty people were arrested in the city overnight, which police say is slightly more than an ordinary Friday night in the capital.
They includes revellers dressed as a banana, several Reno policemen, a caveman and a Batman.
There was also a set of intoxicated twins who kicked a celldoor for four hours.