Voters resoundingly favoured her as she took almost half of all votes cast for mayor.
It is the first time the district has had a new mayor in 12 years as outgoing mayor Gary Kircher did not seek re-election.
A three-term Waitaki district councillor and former deputy mayor, Mrs Tavendale said she was "incredibly grateful" for the support.
"I’m so excited. I’m quite blown away by all the support.
"I haven’t gone out there and promised a whole lot of big election promises, I’ve tried to just be realistic and be real.
"I’m so thankful that people saw that as a positive."
She won the mayoralty with a 1635-vote majority, receiving a total of 3738 votes, well ahead of challengers David Wilson (2103), Guy Percival (1755) and Kelli Williams (775).
Mrs Tavendale said although there were some "nerves" around the next steps, her focus was on relationships.
"For me, it’s just about building really good relationships and having a really positive direction for our community."
In her previous three terms on the council Mrs Tavendale served on the Local Government New Zealand national council and was actively involved in the development of the Oamaru Harbour bike park and Waitaki Museum and Archive projects.
During the election period she also reactivated her campaign for the land status of the North Otago RSA to be resolved so the "iconic building" could have a future and not continue to be a burden on ratepayers.
Mrs Tavendale said focusing on unity, rather than division to meet "massive challenges" ahead was key, as was working proactively with the "amazing" new council 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.
"There’s just too much division out there these days and I hope to change that," she said.
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.
Before the election, officials rejected the former council’s in-house water services plan, and ordered the council to conduct a full review of the district’s water assets or face ministerial intervention.
Mrs Tavendale said the rejection was "not unexpected", with the DIA concerned about issues with the council’s direction from early on.
"The next few months we must show a willingness to work with others and find the most affordable solution for our community.
"The big one for me is stability. We’ve got so many costs in front of us — we’ve got the water discussion, the whole future for local government and what it looks like is on our radar. It’s so complex and those relationships at national level are really important.
"I’ve got some really cool relationships nationally and I believe we can do some really good things," she said.
Her family, husband Steve and children Josie, 14, and Declan, 12 were "really excited" about her new role.
Her two children had grown up "playing under the council table".
"They did miss it when I stepped down as deputy mayor so they’re really excited to see me step back into that space.
"It’s a massive change for our whole family.
"Steve will be running the cycle business fulltime now, so it’s exciting to start to be able to plan our lives now."
