Mr Cadogan comfortably unseated incumbent Tony Lepper to become the district’s mayor.
He won 5288 votes, more than double Mr Lepper’s 2637.
The third candidate, Martin McPherson, got 1062 votes.
Tim Cadogan’s older brother, Bryan (57), ran uncontested to retain the Clutha mayoralty.
Tim Cadogan (51) said his brother’s achievements as Clutha Mayor were a "major influence" in his running for the role.
"I’ve seen what an impassioned mayor who is part of their community can achieve."
He was taking on the role with "fresh eyes", he said.
"I have done almost two terms on Vincent Community Board, but there’s definitely some learning for me to do.
"I’d talked all the campaign about a disconnect between the [Central Otago District] council and the community. I think my message that it was time for that to change was picked up by people."
The three candidates ran honourable campaigns, giving the district’s people "three really good options to choose from".
Mr Cadogan will not seek re-election on the Central Lakes Trust and will shelve his law practice, keeping only 5% of his practice’s work.
Bryan Cadogan said he was "awfully proud" of his brother.
"It’s a surreal day, the day you first get voted in as mayor. It’s funny, because I knew the emotions that he was going through and it’s almost Shakespearean."
"There’s a camaraderie that is built up amongst mayors. It’s going to be different working with my brother."
Mr Lepper said he "paid the price" for raising rates in parts of the district.
"I’m disappointed, but I think they needed to be done, so I’m perfectly happy with what we achieved."
He did not know whether Mr Cadogan would make a good mayor, but noted the many returning councillors would keep him "on the straight and narrow".
For Mr Lepper, the defeat marked the end of a 27-year career in local politics, including two terms as mayor, "I’ve always been one of those people who says when one door closes another door opens, so I’ll have to wait and see what that door is."
Mr McPherson said Mr Cadogan "hit the note with the ‘time for a change’."
