Arvato Services is part of the €4.4bn (£2.97bn) turnover Arvato Group, the marketing services subsidiary of German media giant Bertelsmann. Arvato Group's other three divisions cover print, storage media and systems.
The acquisition of Moon River and its subsidiary Ion Group is a major step forward for the group in the UK, according to Matthias Mierisch, chairman and chief executive of Arvato Services UK & Ireland.
Mierisch said: "The UK has some of the largest and most sophisticated loyalty schemes in Europe. Ion has been a major player in this market, designing highly intelligent contact strategies.
"Ion gives us a clear and immediate footprint in loyalty and data management here in the UK, which we will grow significantly over the next two to three years."
Arvato's UK services include logistics, customer and data management as well as government and financial collection services.
Moon River has a turnover of £13m and employs 180 people. It acquired Ion Group, which was founded by Ede in 1994, in 2004.