MBO's clients include Esso, Hackett and Royal Mail, and it provides services including direct mail, in- and outbound telemarketing, customer loyalty programmes and database management.
MBO's former managing director Andy Perillo is to stay on as a consultant, while Navigator's managing director Nigel Pearson will head the new company.
According to Perillo, MBO and MoonRiver are a natural fit with complementary services and client base.
"The group's resources in technology and training development will also ensure our services continue to exceed the expectations of our clients," he said.
Stephen Woodward, chairman of MoonRiver Group, said: "MBO is a good strong company, with an excellent client list and we believe that its expertise and business practices mirrors our own, providing benefits to both organisations' clients.
"The merger with Navigator Customer Management is a very logical partnership, and strengthens our ethos of providing end-to-end customer management solutions for our clients."
The other companies in the MoonRiver Group are DirectExcellence, Navigator Technology Solutions; CMSS Customer Management Software; Thinkdata and The Ion Group.
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