In the new role, McCarthy will be responsible for the day-to-day management of the agency, reporting to Chan Suh, Agency.com's worldwide chairman and chief executive.
McCarthy has not yet confirmed a start date, but he is likely to be in place by the beginning of 2009.
His exit from Draftfcb follows that of Logan Wilmont, the former executive creative director, who left in September, and the former chief executive Nigel Jones, who quit to join Publicis in May.
McCarthy replaces Russell Marsh, the former Agency.com managing director, who left in July (see page 3).
Suh said: "Enda is an experienced and dynamic leader who has demonstrated great success in each role he has taken on."
- Perspective, page 21.