Green Island fell apart in the second spell as Dunedin applied pressure and scored six tries and 34 points to win at Miller Park.
Openside flanker Jason Bint was sin binned just before the break when Dunedin led 7-0 and stayed off the paddock for 20 minutes before being recalled by the match officials.
During this time, No 8 Frankie Elisara was given a red card and Green Island played with only 13 men for a period until Bint returned.
Dunedin capitalised on Green Island's indiscretions with some superb attacking play by backs and forwards and took complete charge in the last 20 minutes.
Lock Michael Gurran dominated the line-out and loose forwards Joe Dobson, Andrew Mackintosh and hooker Sam Anderson-Heather were lively.
Shaan Davis was an astute general at first five-eighth and Joe Bradley and Robbie Smith had speed on the wings.
Bradley used his pace to score two second-half tries.
Green Island's inside pairing of Dean Moeahu and Mike Moeahu created scoring chances and hooker Brent Short had a solid game.
Dunedin 41 (Joe Bradley 2, Nigel Graham, Fraser Lau, Joe Dobson, Sam Anderson-Heather, Adam Duhig tries; Robbie Smith 3 conversions), Green Island 0.
Half-time: Dunedin 7-0.
Referee: Scott Taylor.
