Bardega, who has been on a 12-month sabbatical since leaving ARM a year ago, starts his new role with immediate effect, and will report directly to the managing director of Media.Com, Kirsti Wilson.
Bardega joined ARM as the head of digital in June 2004, but then moved to a more central role within the agency.
His role at ARM included responsibility for growing All Response Media Digital as a separate business with its own client base.
Before ARM, Bardega was the head of strategy at WPP's digital agency, Outrider, part of Mediaedge:cia. Bardega's other roles at Outrider included a spell as communications planning manager.
Media.Com has hired 32 people this year on the back of wins that included the Royal Bank of Scotland, which it landed in July.
It has also created a search and affiliates team, and expanded its activity in areas such as podcasting and mobile, as well as in-game advertising.