Tasman won 29-27 after leading 22-13 at the break.
The game had two yellow cards and a red card to Tasman centre Levi Aumua after he put in a nasty tip tackle in the second half. It was a willing encounter and plenty of tired bodies in the game.
Tasman skipped out to 29-13 early in the second half through a penalty try and held off a fast finishing Otago.
The home team came back in the final 10 minutes but could not catch Tasman.
It scored tries through Sio Tomkinson and Sione Teu in the final few minutes but could not put the final nail in the coffin.
The game ended before the hooter went which puzzled a vocal crowd.
The best for Otago was lock Josh Furno and flanker James Lentjes while Tomkinson was busy in the Otago midfield.
Tasman 29 (Will Jordan, James Loew, Levi Aumua, penalty try; Mitch Hunt 2 pen, con); Otago 27 (Tei Walden, Sio Tomkinson, Sione Teu tries; Fletcher Smith 3 con, 2 pen) Halftime: 22-13 Tasman
