Dialogue DLKW, the digital, direct marketing and sales promotion agency, will cease trading as a separate entity and will combine its services to form a "single, multi-disciplinary communications agency".
DLKW said that the merger would not affect any clients.
As part of the deal, the partner James Pool will join Alex Kuropatwa as the joint managing directors and Tom Knox becomes the deputy chairman.
The head of sales promotion and point-of-sale, Niki Cook, becomes the deputy managing director, while the group strategy director, Richard Warren, becomes the communications strategy director.
Greg Delaney, the chairman of DLKW, said: "We have brought the disciplines closer together so that the brands we represent can speak with the same voice and from the same brand understanding."