Player/coach Isireli Baleitavuki said his team refused to panic running in three second-half tries to Napier's one to take the title.
Earlier, Ngamatapouri had beaten Old Boys University 12-5 in their semifinal with a vocal band of supporters cheering them on, while Napier Pirates had defeated home team Wainuiomata 17-10.
Ngamatapouri have had an awesome first season back in both 15 and 7-aside codes in 60 years.
After finishing runners-up to Hunterville in the Tasman Tanning Wanganui Senior 15s competition, Ngamatapouri had recent tournament wins in the Wanganui club 7s and Manawatu Fijian 7s events.
They will be back to Wainuiomata on Waitangi weekend to contest the National Club 7s Championship in February.
In the meantime, Baleitavuki said there would be little downtime in the coming weeks with the Wanganui 7s side, which has a Ngamatapouri influence, heading to the Central Zone Regional competition in Levin this weekend in an attempt to qualify for the Pub Charity National regional tournament in Rotorua on January 16.
"There won't be much celebrations for us - no barbecues, only healthy food."