Buller scored the only try of the game in just the seventh minute, when first five-eighth James Lash floated a superb pass to second five-eighth Peni Nabainivalu, who drifted through the defence to score an unconverted try.
North Otago first five Stephen Fenemor kicked three penalties in the first half, but Buller pushed to an 11-9 lead at the break, through a long-range Andrew Stephens penalty and a Lash penalty.
Lash added two more penalties in the second half to seal the four points for Buller.
North Otago coach Mike Mullins was disappointed and said he expected better from his side after its tour of the Pacific Islands.
''We couldn't get into any rhythm. Our breakdown was as bad as it can get in terms of accuracy,'' Mullins said.
''It's hard to play rugby if you don't have the ball. Buller just seemed hungrier. There's an old adage about who wants to win the most, and they obviously did.
''The Buller defence was such that we just couldn't get into the structure we wanted to use.
"We conceded penalties at crucial times that helped relieve the pressure on the opposition and rugby is about how much pressure you can put on the opposition. Simple, soft penalties just take that pressure off.
''I'm disappointed, especially for the players. Just looking at their body language showed that they knew they could have done better.
''But we can only spend so much time on what went wrong.
"It'll come down to how we train this week in terms of our preparation and what selection mix we go for.
"No-one is guaranteed a place in the team and that's right from the outset.''
Locks Matt Mullins and Tom Rowe did some positive things in the lineout, along with Josh Clark, while young tighthead prop Thomas Shields came through his first-class debut well, as did loosehead DJ Sears-Duru.
Right winger Simeli Koniferedi always looked for work but the rest of the backline was stifled by its own inhibitions and the Buller defence.
The Buller side was prepared to run the ball. Midfielders Nabainivalu and Mike Lealava'a looked dangerous, No 8 Tai Ratu was always a danger and locks Craig Moore and Morgan Eames were worthy competitors at lineout time.
In the other Heartland Championship games, South Canterbury beat Wanganui 31-18, Mid Canterbury came from behind to beat West Coast 52-27, Poverty Bay thumped East Coast 52-12, King Country upset Wairarapa-Bush 32-13, and Horowhenua-Kapiti and Thames Valley drew 19-19.
- Terry O'Neill
Heartland Champ
The scores
Buller 17
Peni Nabainivalu try; James Lash 3 pen, Andrew Stephens pen
North Otago 9
Stephen Fenemor 3 pen
Halftime: Buller 11-9.
