The London agency won the business following a competitive pitch. In the past the retailer has worked with McCann Manchester on part of its digital business.
Razorfish London will work alongside C&A’s European advertising agencies, DDB and Tribal Amsterdam, which were appointed the account last year.
Bart Brenninkmeijer, the chief brand officer and member of the European executive board C&A Europe, said: "Razorfish fully understood our vision of a customer-oriented, digital C&A universe with clear structure and user-friendly, seamless navigation."
C&A, which no longer has stores across the UK, has more than 1,500 shops in 20 other countries and an active e-commerce operation.