Poor finishing had cost Otago dearly in earlier, tight losses to Wellington and Southland but they had no complaints on that score at Carisbrook in Dunedin.
The foundations for their first win of the season were laid in the first half when they crossed for three tries to lead 22-9 despite surrendering the possession and territory stakes to North Harbour.
While the visitors were reliant on the boot of first five-eighth Luke McAlister for their points, Otago prospered via the tryline which was visited by lock Tim Donnelly, wing Karne Hesketh and fullback Ben Smith.
Hesketh initiated the first of the tries in the 13th minute when he used his step and strength to make ground and maintain possession up the right flank.
Two phases later Otago outnumbered North Harbour on the left flank where Donnelly strolled across for a soft opener.
Hesketh scored the next himself, picking up a loose ball near the 22, standing up fullback Jack McPhee and muscling his way across the line despite the close attention of two defenders.
Just three minutes later Otago extended their lead when Smith chased a kick ahead and charged down McPhee's attempted clearance.
The match lost a lot of its shape for much of the third quarter until North Harbour found some continuity, camping inside the Otago for a long period midway through the spell.
The Otago defence was determined and it needed to be as North Harbour were twice denied, firstly when skipper Anthony Tuitavake was held up over the line then a touchdown by flanker Malakai Ravulo was ruled out due to a forward pass by McAlister.
But these were to complete a very brief highlights reel for North Harbour, who generally added little to the contest.
McAlister's three penalties were to be their lot, and although he missed another three attempts most his shots were from long range.
Otago made a brief excursion deep into North Harbour territory late in the match and they made it count when a tap penalty from 5m was turned into a bonus-point fourth try to Noakes after a clever offload from Donnelly.
