The 33-year-old took five for 23 — his first twenty20 five-wicket bag — to help Canterbury secure a seven-run win.
The home side posted 157 for seven thanks to Peter Fulton and Henry Nicholls, who combined in a 109-run- stand for the third wicket.
The Volts (150 for nine) appeared to have the run chase under control until Hilfenhaus swung the match in the penultimate over.
He trapped the dangerous Jimmy Neesham lbw with a cracking yorker and also picked up the scalp of Brad Wilson when the experienced right-hander hit a pull shot to midwicket.
Otago was left needing 17 off the last over from Ed Nuttall but fell seven runs short.
"That lbw was probably the key wicket in the game," Otago coach Rob Walter said of Neesham’s dismissal.
"A guy like Jimmy Neesham would back himself to get 12 an over and put two balls over the boundary out of six, so that was a big loss.
"And Brad Wilson had batted beautifully up until that point also. That probably took the firepower away and you lose by seven — that’s the nature of T20 cricket."
The win lifted Canterbury to three wins from six games. Otago has the same record but held on to third place courtesy of a superior net run rate. The teams will play again in Alexandra on Boxing Day but Otago will be without the services of key batsman Neil Broom and classy all-rounder Neesham.
Earlier, Canterbury elected to bat but was immediately under pressure with Chad Bowes hitting a soft catch to mid-on in the opening over from Anaru Kitchen.The home side suffered another setback when Tom Latham was run out thanks to a direct hit from Hamish Rutherford.
But Fulton and Nicholls set about the salvage mission with plenty of the class and got Canterbury through to 117 for three from 14 overs.
Fulton clubbed 64 from 43 before he miscued a pull shot and was caught.
By then, Canterbury was a track for a decent score but Neil Wagner and Neesham combined to run through Canterbury’s middle order of Andrew Ellis, Cameron Fletcher and Tim Johnston, while Christi Viljoen snaffled the dangerous Nicholls for 52 thanks to a stunning catch by Michael Bracewell. It was "an eight out of 10" bowling effort from Otago with Neesham and Viljoen both finishing with two for 25.
Otago’s reply faltered when Kitchen and Broom both got out early. But Rutherford (38 off 35) and Bracewell (38 off 33) added 60 for the third wicket. Neesham and Wilson were held back to close the innings and the pair added 40 runs from 21 balls.
Then Hilfenhaus returned and sent down that yorker which changed the course of the match. In the other match, Northern Districts beat Central Districts by 10 runs at Seddon Park.
