The two agencies will provide communications strategy, data analysis and creative development, segmentation, production and management of campaigns.
Initially, this will focus on the UK, but has the potential to expand into Europe and the Far East.
The bookmaker has previously handled much of its communications in-house and used agencies including Unique Digital, HHM Communications and Geoff Howe Marketing.
Ladbrokes wants to focus on areas of growth for its business - horse-racing, sports betting and particularly the competitive online gaming market. "For Ladbrokes, this represents getting very serious about online," David Eastman, the managing director of Agency.com, said.
The account will be shared between the two Omnicom-owned businesses but will be managed by Agency.com, the agency originally approached by Ladbrokes.
The two agencies have worked together before but this is the first time they have pitched as partners. "We are getting more and more requests to pitch with DM agencies," Eastman said.