The agency won the business without a pitch and will be responsible for creating a series of campaigns to help raise awareness of the fund-raising schemes.
Details of both initiatives are currently being kept under wraps, but they both involve innovative product launches.
The work will launch in June and will focus heavily on digital media.
Cancer Research UK already works with a number of agencies on its advertising business, including Abbott Mead Vickers BBDO, OgilvyOne and Essence.
Last year, the charity appointed Rapp to handle the integrated advertising for its £2m "race for life" account.
Brendan Tansey, the chief executive of Wunderman, said: "It's great to be working with the UK's premier charity on projects that break new ground for such a famous brand".