Josh Ioane kicked a 77th minute penalty from the sideline to give Otago a 22-20 victory at Forsyth Barr Stadium.
Otago had trailed 17-0 after Canterbury capitalised on an intercept and kick deflection in the first half.
However, Otago fought back through a try to Freedom Vahaakolo and an Ioane penalty made it 17-10 at the break.
From there Otago dominated the second half.
It had all the ball and territory and while the Canterbury defensive line held, Ioane kicked four penalties to get Otago over the line.