Of those arrests, 15 were felonies and 11 were misdemeanors, Sgt. Jason Dwyer said.
The unofficial Mardi Gras celebration is not an organized event, but is known to draw rowdy crowds.
Dwyer said the troublemakers have tended to be the minority in the past few years.
"Generally, the biggest reason that things have quieted down this year is that people just want to go down to have fun, not commit a crime," Dwyer said.
There was one serious incident during Tuesday night's celebration in which a 21-year-old woman was assaulted and knocked unconscious in the Third Street parking structure, Dwyer said. She was taken to a hospital with injuries that were not life-threatening.
The suspect was not identified, he said.
Most of the arrests were for probation or parole violations, outstanding warrants, or illegal weapons. Six of the people arrested were not San Jose residents.
Last year's celebration saw the same number of arrests.
