ACT president Chris Simmons says the board has unanimously endorsed Don Brash as the new leader of the party.
Dr Brash formally took over the leadership of ACT from Epsom MP Rodney Hide after a series of meetings on Saturday.
The board met in Auckland and accepted Dr Brash's application to be a member of the party.
ACT's five MPs then unanimously endorsed a recommendation from Mr Hide that Dr Brash take his place as leader.
The board reconvened, and ratified the decision, before having a lengthy discussion with the new leader.
Dr Brash acknowledges there were concerns within the board about the way he went about his leadership bid, and says he's not surprised there was a degree of concern about his challenge given that most of the board had never met him before.
He says he had a constructive discussion with the board on Saturday and they came to a good understanding and a common view of where the party has to go.
ACT president Chris Simmons had been critical of Dr Brash, but says the board fully supports the new leader. He says Dr Brash will bring new energy to the party ahead of the November election.
The position of deputy leader John Boscawen was not on Saturday's agenda but will be discussed over the next few days.