Two from Fianna Fail and one Independent will take up the roles.
Three members of Offaly County Council will sit on the new board for the Tullamore Arts Centre.
Cathaoirleach Declan Harvey and Danny Owens from Fianna Fail and Independent cllr Sean O'Brien were appointed at Monday's monthly meeting.
Work on the new 220-seat theatre remains ongoing, with an opening date of July 2022 mooted at the moment.
It was also confirmed that the current board will remain in place until that date.