Napier scored first with a try to blindside flanker George Manson, converted by Berkett, and conceded points for the first time when Hamilton front-row forward Tom McCarthy scored in the 28th minute, at a time Napier were down to 14 with captain Max Ratcliffe on the sideline after being yellow-carded.
Hamilton fullback Payton Spencer, son of former All Black Carlos Spencer, was unable to convert, and Ratcliffe's return became important to the Blues' response, a try to fullback Joshua Augustine four minutes from the end of the first 35-minute half.
A Berkett penalty gave Napier a 15-5 buffer 17 minutes into the second half, but it was narrowed to three points when Hamilton centre and captain Aki Tuivailala scored with 12 minutes to go and Spencer added the conversion.
The heartbreaker was Hamilton right wing Caelys Putoko's try with 69 and a half minutes on the clock, not only winning the title but also retaining the Moascar Cup, the Ranfurly Shield of schools rugby.