The Volts bowled well to restrict Canterbury to 152 for eight. But what should have been a fairly straightforward chase morphed.
A crowd of 1200 watched as the Volts slumped to 34 for three and then 83 for six.
They were eventually restricted to 136 for eight.
Canterbury legspinner Todd Astle helped choke the Volts' efforts to catch up with the run rate. He went for just 16 runs from his four overs and picked up the wickets of the dangerous Michael Bracewell for 21, and trapped import Tom Beaton lbw for a golden duck in his debut game for Otago.
Seamer Kyle Jamieson was impressive as well with two for 19 from four overs.
Some lusty hitting from Otago allrounder Christi Viljoen (34 not out from 22) at the end of the innings cut the final margin.
The loss means Otago (12 points) drops to fourth with three wins from seven games.
Coach Rob Walter felt his side would need to win its remaining three games to make the playoffs.
``I think it is very simple. We've got to win all three, don't we, if we want to have a chance,'' Walter said.
``Losing those three early wickets did not help and then from there we just struggled to catch up. But the spinners in the middle really pegged us back.''
Earlier, Canterbury opener Chad Bowes clipped the first ball of the match through point for four but his partner, Cameron Fletcher, had a lot less luck.
He tried to clamp down on a yorker from Anaru Kitchen and managed to get some bat on it, only for the ball to dribble on to his stumps and bowl him for one.
Peter Fulton had even worse luck midway through the innings. Andrew Ellis thumped a drive back down the ground, which Josh Finnie tried to stop but managed to deflect on to the stumps.
Fulton's innings was cut short on 19.
But it was Viljoen who picked up the key wicket. He lured the in-form Henry Nicholls into a lofted drive but the batsman only got it as far as Hamish Rutherford at mid-on.
Still, Canterbury was reasonably placed after 10 overs at 75 for three.
Bowes was playing nicely and reached 50 off 36 balls. But he got down on one knee and tried to paddle a delivery from Nathan Smith to the square leg boundary and was hit on the helmet. He took a short break to shake off the blow but holed out the next ball for 54.
Experienced allrounder Ellis top-edged a pull shot just as he was starting to look dangerous. His departure for 23 off 18 robbed the visiting side of a hard hitter.
Otago owned the final four overs with Neil Wagner and Viljoen combining to restrict their opponent to just a further 23 runs.
Wagner finished with two for 20 and Viljoen one for 23.
Otago's chase started unravelling almost immediately. Kitchen got a touch to a legside delivery in the opening over. Then fellow opener Rutherford spooned a leading edge to square leg.
Next Derek de Boorder, who bats up the order when there is a crisis, was bowled for 16 after an eventful 12-ball stay.
Otago got in deeper when Bracewell skied a catch to mid-on. The desperately needed partnership never materialised. The Volts were left needing 59 from the last five overs but could only manage 11 from the next two. Viljoen finished the innings in style with a four and six to trim 10 runs from Canterbury's winning margin.
In yesterday's other game, Central Districts beat Wellington by six wickets at the Basin Reserve.
