Nick Tweddle, a long-term thorn in the side of the board, was elected along with high-profile architects Claire Wright, of Wright and Wright, and John Assael, of Assael Architecture.
Other additions include Peter Stewart, the former director of design review at CABE, who is expected to be a close ally of the newly elected president-elect Sunand Prasad.
The two other new councillors come from opposite ends of the age range; veteran campaigning architect Sam Webb and outspoken young architect Pascale Scheurer.
The six elected came in this order, by number of votes received:
Tweddle, who was one of the founders of the ARB reform group, said he was 'extremely delighted' to have won, and to have come top.
It is interesting to note that I stood for the RIBA on an ARB Reform ticket including traditional standards,' he said. 'This delivered the highest vote.
'I hope this election result enhances and underlines our own mandate for ARB Reform,' he added. Working within the RIBA I am confident our cause will have an even wider audience and hopefully a little influence, in a constructive atmosphere.'