PHD Confidential won after a three-way pitch against MindShare and Starcom.
Its first task will be to handle planning and buying for a summer launch campaign for Iammoving, which offers an address-changing service.
The facility, which has more than 500,000 users, is free to home movers and notifies all organisations of their move.
Activity will include tactical press and online executions targeting autumn house- hunters and students moving to university or into shared houses. Creative will be handled by an in-house designer at Iammoving.com.
Eileen Rutschmann, the chief executive of Iammoving.com, said PHD Confidential won "because the team demonstrated a strong forensic approach to detail and delivered the solution with energy and enthusiasm".