Singer and guitarist Ollie McLean (16) said the band was "very surprised and very happy" to win, at a bouncing Queenstown Memorial Centre on Saturday night.
"We really didn't think it was going to be us - there were so many great bands there," he said.
The Trainsurfers, McLean, bass guitarist Dillon Bochier (15) and drummer Cameron Kennedy-Grant (15), played two original tracks - The Southland and You Don't Know Me.
They are blues-rock tracks, inspired by the likes of Hendrix, Muddy Waters and The Rolling Stones, McLean said.
Like the other regional winners, they will now put together a video entry with the hope of making the national finals in Auckland in September.
Wakatipu High School musicians dominated the top placings in the band category, The Trainsurfers followed in second by Haven, and No Man's Land in third.
No Man's Land's Hannah White slayed her way to the best musicianship title.
But Wanaka's Mount Aspiring rockers Moss On Rock took the ZM People's Choice award, while Mount Aspiring was also judged to have the best vocalist in Liquid Breakfast singer Luca Georgalli and the best lyricist in Owen Lea, who won the APRA Lyric Writers' Award for Back Door Intention.
Honey by Wakatipu High School band Murphy's Law won best song.
Tyrone Henderson, another WHS pupil, previously took the solo/duo Central Otago regional title, with WHS pupil Greta Balfour second.
McLean said The Trainsurfers have been playing together for a year, including some pub gigs.
"I hope we stay together - maybe move to Dunedin, play pubs."
Meanwhile, Gore High School's Murder on Venus was best band in the Southland regionals, with band member Hamish Waddell winning the musicianship award.
Verdon College's Destiny won Smokefree Tangata Beats, and Maggie Townley, also of Verdon, was solo and ZM People's choice winner. Central Southland College's Zookiniz won best song, Menzies College's Back On Road won the APRA Lyric Writers' Award for Turn Your Life Around, and Southland Boys' High School pupil Michael Karesa won best electrotonic assistance.
