Media Square is to spend all the cash on reducing its debt to below £20m. The sale follows that of its sponsorship agency, Karen Earl Sponsorship, for an undisclosed sum to Engine Group, which also owns WCRS, in November.
Jeremy Middelton, chief executive of Media Square, said: "I believe that Tangozebra and DoubleClick will represent a remarkably strong force in the fast developing online advertising business, both in the UK and internationally.
"DoubleClick is the preferred partner of leading companies worldwide for a full range of advertising solutions and has offices throughout the USA, Europe and the Asia Pacific region. As a leading technology business it is far better equipped to invest in and build on the Tangozebra offering."
Middleton said the transaction represented another step in Media Square's programme of focusing attention on those areas of the business that they believe can grow most successfully.
"The disposal of our interest in Tangozebra represents an exceptional profit over our acquisition cost in November 2005," he said. The agency was one of several acquired from Huntsworth for a total cost of £63m.
Tangozebra reported pre-tax profits of £244,000 and had net assets of £647,000 as of February 2006.
Media Square, which owns direct marketing agency CMW and Dynamo Marketing Communications, has a turnover in excess of £200m and around 1,800 employees.