A Special Costable was assaulted and a number of football fans were spoken to by police after crowd disorder outside Sixfields Stadium.
Police were forced to intervene after Walsall and Cobblers fans became aggressive folliwing the League One match on Saturday.
A Northamptonshire Police spokesman said there were a number of assaults including one on a Special Constable.
The spokesman said a number of people were spoken to and their details were taken. The police investigation is ongoing.
Witnesses, or anyone with information, are asked to call Northamptonshire Police on 101. Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111.