Response One will add to St Ives' data management, direct marketing, field marketing, POS and print services.
Patrick Martell, chief executive of St Ives, said: "The acquisition significantly enhances and extends the data based offering we are able to provide to clients to enable them to maximise return from their marketing campaigns."
Response One employs approximately 70 staff, is headquartered in Bath and has projected revenue of £25m for the year ending October 2011.
It will operate as a subsidiary of St Ives and will continue to be managed by the existing management team from its existing premises.
Patrick Sargeant, managing director of Response One, said: "Our knowledge of how to maximise response from direct marketing media, combined with our insight driven approach to data and our innovative campaign production techniques fits perfectly with St Ives.
"It gives us a wonderful opportunity to strengthen our competitive advantage and satisfy our ambition for growth and expansion."
St Ives was advised by Ingenious Corporate Finance.