The score was tied up 10-10 at half-time, but Otago dominated territory and possession in the second half to win 23-18.
After a poor display at the set-piece last week against Canterbury, the tight five led the way for Otago.
Winning five line-outs off the Northland throw and showing a solid scrum, the engine room ran far more smoothly than it did six days ago.
Lock Tom Donnelly had a stand-out game, showing the All Black selectors he is ready for the next level.
If he was the best man in the dark blue, Highlanders winger Fetu'u Vainikolo was the star for the Cambridge Blues.
He bagged two tries, and the cheque books will be out as teams try to nab the fleet-footed Tongan.
Luckily for the home side, Vainikolo saw little of the ball and he was kept quiet for long periods.
But the weight of possession seemed to tell on Northland, which failed to put together many concentrated periods of attack.
In the second stanza, the home team camped in the Northland half and applied pressure.
Though it scored only one try, to winger Lucky Mulipola, it went close another couple of times, and should have won by more.
Midfield back Aaron Bancroft was stripped of the ball just as he went to dive over the line, while the ball was spilled in a forward drive with the Northland try line exposed.
Otago must learn to be more ruthless when it gets chances, and needs to show more composure in scoring positions.
Mulipola's try came after three attacks on the line, and the Samoan winger could not be stopped as he charged over from about 10m out.
Northland could not come back into the game in the second half, and Otago's defence stood up well off the set-piece.
The first half was a see-sawing battle, with neither team holding on to the ball for long enough to apply pressure.
Daniel Bowden missed two relatively easy penalties in the first 10 minutes of the match.
Those misses looked as if they might prove costly when Northland fullback Jared Payne ran back a poor Toby Morland clearing kick.
He beat a couple of tackles and then passed the ball to Vainikolo, who sliced through two defenders to dive over in the corner.
Otago came back with some vengeance and a good break by Donnelly set up an overlap which had winger Karne Hesketh charging over to score in the Rose Stand corner.
Bowden converted from the touchline to tie the scores up.
Apart from Donnelly, Craig Newby showed he is quickly adjusting to the openside role, while prop Ben Nolan ran hard.
The midfield for the home side was solid, and Hesketh showed some endeavour in his limited opportunities.
For Northland, apart from Vainikolo, who was outstanding, fullback Jared Payne was threatening when he got the ball, while David Holwell had some nice touches, although why he kicked the ball away with a minute to go is a mystery.
Up front, lock Daniel Goodwin got through some work, while openside flanker Joel McKenty was busy at the breakdown.
Otago 23 (Karne Hesketh, Lucky Mulipola tries; Daniel Bowden conversion, 2 penalty goals, Chris Noakes conversion, penalty goal), Northland 18 (Fetu'u Vainikolo 2 tries, David Holwell 2 penalty goals, conversion) Half-time: 10-10.
Crowd: About 2500.
Winger Hosea Gear scored three tries as Wellington maintained its unbeaten run with a 64-7 win over a hapless Counties-Manukau in Wellington last night, NZPA reports.
It had earned its bonus point by the 24th minute when lock and captain Jeremy Thrush scored its fourth try, and it crossed for nine tries in all, with first five-eighth Fa'atonu Fili kicking nine goals from 10 for 19 points.
Wellington finished with a flourish, Gear scoring his third try and replacement Tomasi Palu crossing in the last five minutes.
Wellington 64 (Hosea Gear 3, Serge Lilo, Victor Vito, Jeremy Thrush, Michael Hobbs, Alby Mathewson, Tomasi Palu tries; Fa'atonu Fili penalty goal, 8 conversions), Counties-Manukau 7 (Romi Ropati try, Dean Cummins conversion).
Half-time: 38-0.
Otago 23
Northland 18
