Hyperlink has had a number of suitors over the past few months, which are believed to have included C&W's rival cable firm Telewest.
"We negotiated with a lot of companies and we didn't go with the highest bidder," said Hyperlink's managing director Tim Jenner. "Companies we spoke to included American media marketing companies, traditional US agencies and telcos. We can't continue growing organically at the rate we have been as a privately owned company. The acquisition will help us especially on interactive TV projects for clients, which require large up-front investments."
He added that Hyperlink's headcount would grow from its current 98 staff to 300 over the course of the next year.
The move is the cable company's 26th acquisition of an internet company in the past two years.
Rick Hudson, vice-president of business development at C&W, said: "We have an internet infrastructure but this is a group that programs this up for the business."
Hyperlink, which was founded in 1994, has a net asset value of £1.156m according to last month's management accounts. Its client base is concentrated on the retail, media, finance and publishing sectors.