The match went right down to the wire with Otangarei fullback Sam Henry securing the victory in the last minute.
Otangarei coach John Hunapo said it wasn't a vintage performance, but they got the job done.
"They didn't play that well, we've got a long season ahead but even though we had a win, there's a lot of work we need to do," Hunapo said.
"The boys always think they're in the game but they sometimes lose track of things during the game. It's a mental thing, but we will keep working on it."
Both sides came out firing on defence, providing a feast of big hits and errors in the tackle.
Madisyn Kaka broke the deadlock early as Portland heaped the pressure on Otangarei.
Otangarei then coughed up the ball 40 metres out from their own line, which Portland's Mike Salase gleefully picked up and sprinted over the try line.
Kass Wall's second conversion of the afternoon doubled their lead.
Otangarei piled pressure on Portland, but breaking through their defence was a war of attrition.
Otangarei forced an error from Portland 10m out from the tryline, giving Bjorn Watts the opportunity to cross for a converted try.
Otangarei came out from the break firing as Petero Blake crossed the line after a great set-up play.
Shortly afterwards they broke the line again, this time through Shaquille Ormsby, who passed inside for Shane Herbert to give Otangarei the lead.
Verne Wilson added the extras to extend their lead to four.
Portland were not out yet though as the home side, buoyed by a vocal crowd, scored off a grubber in the corner through Zac Pere to bring the deficit back to six with just 10 minutes left on the clock.
Both sides battled hard before Henry found his way over the line after a pair of big runs from Sepeti Tatau, securing the victory.
The final match of the round saw Takahiwai Warriors proving they are definitely the team to beat again after a 44-6 win over Northern Wairoa Bulls.
The reigning champions were far too clinical for Northern Wairoa and were tough to crack on the defensive end.
Hora Hora Broncos had the bye.