Despite the momentum being against them, it was Bay of Plenty who opened the scoring 10 minutes in when Caleb Piua straightened up close to the tryline and was able to reach out and score in the tackle.
Manawatu squared things up at 6-all when Sheldon Tairea was rewarded for some strong line running and raced through to score in the right-hand corner.
Manawatu kicked a penalty late in the first half to take an 8-6 lead into the break.
Bay of Plenty were down to 12 men for much of the second half when they had a player red carded for dissent.
Manawatu extended their lead to 12-6 before halfback Brooklyn Herewini produced a superb piece of solo play, stepping through the defensive line, beating the fullback and scoring under the posts. The try was converted and Manawatu led 18-6.
Bay's Sean Field scored late in the game and the conversion meant his side were a chance of a comeback, trailing 18-12. However, Manawatu dug in and held on for the victory.
The under-13 boys' tournament was won by Northland, while Waikato produced a clean sweep in the girls' tournaments.
For the teams of the tournament and individual awards, go to the Upper Central Zone Rugby League Facebook page.
North Island Districts Rugby League Tournament Winners
Under-13 Girls: Waikato
Under-15 Girls: Waikato
Under-17 Girls: Waikato
Under-13 Boys: Northland
Under-14 Boys: Waikato
Under-15 Boys: Bay of Plenty
Under-17 Boys: Manawatu