He admitted it would not be an easy job and said he wanted to reconnect with the stakeholders of Otago rugby.
Mr Mains, who ended his connection with Otago rugby at the end of the 2003 season after a messy falling out with players and then Highlanders chief executive John Hornbrook, last night said his election to the board was another rugby challenge to which he looked forward.
Otago District Health Board chief medical officer of health Richard Bunton was also elected to the board.
Mr Mains said in his speech at the union's annual meeting last night - before he was elected to the board - that life in business and rugby was about being accountable.
"The time is right for me, with the experience and the knowledge of this game, that I give something back to the game," Mr Mains said.
"I'm a strong advocate for the new stadium and think it will be great for the city.
And to do that, the team and Otago must be successful.
"There are no excuses.
"It is not about rugby politics.
It is about Otago rugby survival and regaining our position as the leading provincial side in the Highlanders province.
"I am a man of action, not a man of words.
"[On] Two occasions I have come along to rescue Otago rugby and I have done the job with total dedication and commitment.
"Both these times I have been successful and that is the level of commitment I would bring to the board."
Mr Mains said after the meeting he had not thought about being chairman and had just wanted to concentrate on getting on the board.
Chairman Ron Palenski confirmed at last night's meeting he was standing down after seven years in the role.
The new chairman will be elected by the board at its first meeting, expected to take place in a couple of weeks.
