Mr Shadbolt received 11,590 votes ahead of closest challenger Tom Conroy, who received 6109 votes.
It is the 69-year-old’s eighth term as mayor.
"Often I just get one long-shot person, or I’ve even got in unopposed in one election, but this one I was up against a television producer and an investigative journalist, so it was pretty hard going."
It was "heartening" to win with a comfortable margin in what he feared was a tighter race.
"I thought maybe splitting the vote might be the critical factor, but it proved not to be the case. I got more than the other two combined."
The Invercargill City Council has four new councillors: Toni Biddle, Alex Crackett, Lesley Soper and Allan Arnold.Ms Biddle, a local music identity, was the third highest polling councillor.
The highest polling, Darren Ludlow, would be deputy mayor again in the new term, Mr Shadbolt said.
Karen Arnold, a former journalist who polled in third place for mayor, was the seventh-highest polling councillor candidate.
Other returning councillors are Lloyd Esler, Rebecca Amundsen, Graham Lewis, Ian Pottinger, Lindsay Thomas and Graham Sycamore.
Three sitting councillors were voted out: Lindsay Abbott, Neil Boniface and Peter Kett.
Council veteran Alan Dennis did not stand for the city council but was re-elected to the Invercargill Licensing Trust Board as the fifth-highest polling candidate.
The other ILT members are (in polling order) Paddy O’Brien, Suzanne Prentice, Mike Mika, Angela Newell and Sean Bellew.
In Southland District Council, Gary Tong was elected for a second term as mayor against a reluctant challenger.
Mr Tong received 6873 votes and Steve Fagerlund received 885 votes. Mr Fagerlund had said he no longer wished to stand after the nominations closed, but his name remained on the voting papers.
"We have some new councillors and I am keen to get to know them and their interests. I want to take the time, too, to acknowledge the work that the two retiring councillors, Lyall Bailey and Rodney Dobson, did for Southland District," Mr Tong said in a statement.
The Southland District councillors are John Douglas, Ebel Kremer and Brian Dillon, unopposed, in the Mararoa-Waimea ward; Bruce Ford in the Stewart Island-Rakiura ward; George Harpur, Nicholas Perham, Stuart Baird, unopposed, in the Waiau-Aparima ward; Paul Duffy and Julie Keast, unopposed, in the Waihopai-Toetoes ward; Neil Paterson, Darren Frazer, and Gavin MacPherson in the Winton-Wallacetown ward.
