The Taniwha led 10-3 at halftime thanks to a Derek Carpenter try and should have scored twice more late in the spell but they were let down by handling errors.
A try to Filipo Levi and the boot of Hayden Cripps and Andrew Goodman saw Tasman reel in the Taniwha after openside Jach Ram was sinbinned for detaching from the scrum as Tasman tried to engineer a pushover try.
Tasman scored 11 points while Ram was off the field but upon his return he continued to secure turnover after turnover and despite the indiscretion, it was his best game in the Cambridge Blue.
Turnovers kept Northland in the game, with Rene Ranger also securing his share but it was team effort for the Taniwha with all the players, including the reserves, digging deep for the win.
Tasman 17 (Filipo Levy try; Hayden Cripps 3 pens, Andrew Goodman pen) Northland 20 (Derek Carpenter, Mateo Malupo tries; Ash Moeke 2 cons, 2 pens).