Andy May joins as a consultant, with a remit to help clients' digital engagement and media relations.
He will work with Open Road's clients Research in Motion (the makers of BlackBerry), Universal, Vevo and Bowel Cancer UK.
May reports to Martin Le Jeune, a founding director at the agency.
May's criticisms of how the defeated Yes campaign was run were heavily quoted in the national media.
He has also worked for Amnesty International, the Joseph Rowntree Trust and the Liberal Democrats.