The six-wicket loss in cold, blustery conditions was the fifth straight loss in the twenty20 campaign, and leaves the Volts firmly entrenched at the bottom of the competition.
Chasing Otago's 134 all out from 19.1 overs, the Stags were in control throughout the chase and got home off the first delivery of the final over, when Will Young smashed Jacob Duffy to the fence.
Young finished on 39 from 22 deliveries and was instrumental in guiding the Stags to their first win in almost two years.
Volts fans might think they have it tough with five straight losses, but the Stags were riding a 12-game losing streak into yesterday's game, having not won a game since December 29, 2012, against the Northern Knights.
Opener George Worker whacked 47 off 30 balls to get the Stags off to a rollicking start, but Dirk Nannes and Nathan McCullum pegged things back with a few wickets in the middle.
When Nannes, who picked up two for 23 off his four overs, dismissed Jamie How for 18, the Stags still needed 36 runs off the final four overs.
However, Young made sure of it with a flurry of boundaries, including a towering six off Nick Beard into the Highlanders' training paddock.
Jesse Ryder was at his miserly best in the loss, taking one for nine off his three overs. Volts coach Dimitri Mascarenhas, who is still searching for his first win since taking over at the start of the season, felt his side came up short with the bat.
''It's a shame, we just didn't get enough runs in the end. We were probably 20 short. I thought 155 or 160 would have been a good defendable score.
''At least our bowling was better, so there are some positive signs. But we just can't string the batting and the bowling together on the same day,'' he said.
While former captain Derek de Boorder top-scored with a brisk 45 from 30 deliveries in Otago's first innings, he was one of just three players - the others were Ryan ten Doeschate (28) and Iain Robertson (25) - to go past 10.
''Derek played beautifully, but he will be disappointed he didn't go on and get 60 or 70, and it probably would have won us the game if he had,'' Mascarenhas said.
''We have identified that we are just not winning the crucial moments, and in twenty20 cricket you have got to win the crucial moments. We lost wickets at crucial stages when we needed to kick on.''
While heavy showers came and went throughout the day, the match started on time and the rain stayed away for the match. However, a blustery southerly made it hard to defend at one end of the ground, Mascarenhas said.
Otago must now regroup for the first of its last five games, against the Canterbury Kings in Christchurch on Sunday.
''Obviously we have got some hard work to do, but the guys are up for it and hopefully we will put in some good performances,'' the Volts coach saidOtago's innings never really gained any traction, with danger man Ryder caught behind in the first over after smacking a quickfire 10.
Aaron Redmond was run out for the second time in the twenty20 campaign the following over when Seth Rance threw down the stumps from square leg, leaving the Volts in an early hole at 11 for two.
It only got worse when Adam Milne sent Michael Bracewell's leg stump flying with his first delivery of the match, leaving the Volts 31 for three after 4.1 overs with de Boorder and Iain Robertson at the crease.
On his way to 45, de Boorder got a lifeline on 12, when Ajaz Patel shelved a regulation catch at third man.
The wicketkeeper-batsman rubbed salt into the wound the following delivery, guiding an Adam Milne delivery over Patel's head for six.
At 97 for five with seven overs left, 150 was still a possibility. However, regular wickets stifled the flow of runs and the Volts limped through to a below-par total.
While de Boorder got close, only Ryder has scored a half-century for Otago in the first five matches of the competition.
Milne was the pick of the bowlers, finishing with three for 30 off his four overs, including a maiden wicket.
In the day's other game, the Northern Knights unseated the Canterbury Kings at the top of the competition with a 20 run win against the Kings in Christchurch.
After scoring 184 for six off its 20 overs, the Knights restricted the Kings to 164 for nine in reply.
