Liberty said it would buy the unit, Base, via its Belgian subsidiary Telenet in April for 1.325 billion euros ($1.48 billion).
The Commission, which acts as the competition authority in the 28-member European Union, said it had cleared the deal after Liberty agreed to sell Base's stake in Mobile Vikings, an operator which does not have its own network, and to transfer subscribers of Base's JIM Mobile brand to Belgian company Medialaan.