It claimed an impressive 4-3 win over the Stampede in Queenstown to win the Toa Kauhanga Riri Toa trophy, the Ranfurly Shield of New Zealand ice hockey.
The win came in dramatic circumstances, Brandon Egli scoring the match-winner with five seconds remaining.
It followed a 5-2 loss to the Stampede on Friday.
The trophy is contested in the second game of each home double-header.
That means the Thunder's first defence of the trophy will be against the Canterbury Red Devils on July 14.
The Red Devils have the most successful defences since the trophy's inception in 2012 with 12.
It is the first time the Thunder has won it, ending the Stampede's run of four defences.
The win also leaves the Thunder tied in third on nine points on the national league table, although it has played two more games.
However, it has a bye this weekend, giving the Stampede a chance to pull away as it hosts the Botany Swarm, which is one place ahead on 10 points.
The West Auckland Admirals lead the competition on 12 points.
