Sergeant Sam Parata from Tokoroa Police said the fighting, which involved people throwing bottles and cans, started after a party in Kelso Street.
He believed gatecrashers who arrived at the alcohol-fuelled party sparked the fighting. He didn't think it was gang-related.
Some of those arrested will appear in court on disorderly and fighting charges - others will be issued with warnings.
The injured teen was initially thought to be critically injured but a Waikato DHB spokeswoman said he was stabilised in the emergency department.
No further details as to the extent of his injuries were available.
A witness, who didn't want to be named, said the police had cordoned off a large portion of the road where the party was taking place.
Two ambulances were seen at the scene along with three or four police cars.
A woman who lived on a nearby street reported hearing some shouting, but was unable to see much from where she was.
"I heard things, I heard a young man say, 'oh you shouldn't have done that'.
"There are some people out there, but I can't see much, they are just talking. I can see car lights."
The woman said she'd also heard a siren go past not long after hearing the shouting.
She said there were often large disturbances in the area on the weekends, with parties getting out of control from time to time.
In May a gang brawl inside the Tokoroa District Court forced the judge and staff to lock themselves in a safe area. The fight made the walls move.
At around 10:30 a police spokeswoman said the street had been cleared.
However, she said additional resources had been sent to be on "stand-by" in case of another incident.
She was unable to confirm exactly how many police were at the scene.
