The much-needed win has helped keep their playoff prospects alive and shake off some doubt following a string of disappointing results.
Jona Nareki looked more like the power-packed threatening winger Otago crowds have come to love.
Sam Gilbert's return brought a reassurance at the back which has been missing in his absence.
And the tight five can take a bow after another solid shift.
There was still some vulnerability around the ruck which Otago will need to address.
But this was easily their best performance of the season.
With the small crowd barely settled in their seats, the home side swung the ball to the right and then came back left to first five Ajay Faleafaga.
He put in a deft kick pass for Nareki, who found lock Will Tucker steaming up on the inside and his angled run carried him the required 15m to score.
Gilbert added the conversion from the sideline to make 7-0 after two minutes.
Beautiful rugby.
Northland responded with a penalty to Rivez Reihana and they snaffled several turnovers to heap some pressure on Otago, whose fragility at the breakdown has been an issue all season.
But Otago were able to lean on their scrum to wiggle out of trouble.
Gilbert nailed back-to-back penalties before Northland forced another turnover and got some traction close to the ruck.
They looked to have muffed the opportunity when the ball sailed over the back of a 5m lineout.
Jack Leslie collected it and tried to hoof it into touch, but sliced it badly. It spun end for end, travelled all of about three metres and straight into the arms of Heremaia Murray, who will probably never score an easier try.
Northland were trailing 13-8 at the break and found themselves down to 14 men when Jack Goodhue was sent to the bin for getting himself offside at a critical moment.
The Taniwha were under siege and eventually cracked out wide. Nareki went over in the corner following a sustained period of attack.
Murray came up with a stunning effort to cut the gap.
He scooped up some loose ball at the ruck and burst free with just one to beat. Just as well he beat his man because there were several unmarked teammates to his left he did not seem that fussed about using.
Otago got back in control when they shoveled the ball along the line and Jake Te Hiwi went in untouched with seven minutes remaining.
In the other fixtures today, Tasman beat Taranaki 29-18 while North Harbour rolled Manawatū 48-29.
On Saturday, Bay of Plenty edged Hawke's Bay 38-35, Counties-Manukau beat Southland 39-29 and Auckland clinched a 36-29 win against Canterbury.
The scores
Otago 30
Will Tucker, Jona Nareki, Jake Te Hiwi tries; Sam Gilbert 3 con, 3 pen
Northland 15
Heremaia Murray 2 tries; Rivez Reihana con, pen
Halftime: 13-8
