Voters resoundingly favoured her as she took almost half of all votes cast for mayor.
A three-term Waitaki district councillor and former deputy mayor, she was "incredibly grateful" for the support.
"I’m so excited. I’m quite blown away by all the support.
"It’s one of those moments where it feels like everything has just fallen into place.
"It's such a long process that you never really know where you stand, so to see a relatively good margin is really exciting.
"For me, it's just about building really good relationships and having a really positive direction for our community.
"There's just too much division out there these days and I hope to change that," she said.
She received 3279 votes, ahead of challengers David Wilson (1812), Guy Percival (1557) and Kelli Williams (697).
Mrs Tavendale said outgoing mayor Gary Kircher had put his "heart and soul" into the role and she thanked him for the opportunities he gave her in their shared time at council.
While Mrs Tavendale said "massive challenges" lay ahead for the council, especially in water services delivery, but she was confident in the new team.
"The best thing we can do right now is to build a good team and to make the best decisions we can in front of us.
"It's about trying to find ways to build a more stabilised council and get things as affordable as possible."
Mrs Tavendale said her family, husband Steve and children Josie and Declan, were "really excited" about her new role.
"It's a massive change for our whole family.
‘Steve will be running the cycle business full-time now, so it's exciting to start to be able to plan our lives now."
In the Waihemo ward, Frans Schlack (379) defeated Garry Dodd (223) and Gervais G O’Reilly (121), while in the Corriedale ward, John McCone and Sven Thelning were elected unopposed.
In Ahuriri, Brent Cowles was elected unopposed.
In Oamaru, adding to a strong female representation at council, Rebecca Ryan topped the polls (2609), hot on her heels was Courtney Linwood (2574), followed by Jeremy Holding (2476), Jim Hopkins (2419), newcomer Dan Lewis (2174) and Hana Fanene-Taiti (2000).
Cr Ryan, who was back for her second term, said she was "incredibly grateful for the support" and "looking forward to doing it all again with a new-look council".
