The company also announced that it is to bring forward its recruiting plans for Shannon, Co Clare, announced by the Tanaiste, Ms Harney, last November, where it now has an immediate requirement for 105 people.
The firm at the centre of the takeover, Knxus, provides call centre services for companies that do not want to establish their own centres. Its existing 175 staff in Castlebar will be retained.
Contact Partners provides outsourced sales and customer care services for companies in the financial services, telecoms and government sectors, as well as general business in Ireland and the UK.
It is a privately owned company, majority owned by Netdecisions Group, a technology solutions provider.
The company's chairman Mr John Mayo said the Castlebar acquisition would allow Contact Partners cope with new business in Ireland and the UK.