The agency won the business after a pitch against MindShare and Carat. Incumbent Universal McCann did not repitch for the account.
MindShare had been the favourite to win the business because of WPP Group's relationship with Sky via its creative agency HHCL/Red Cell.
MediaCom's win comes ahead of increased marketing activity that is expected to see it boosting its above-the-line spend by between 40% and 50%.
However, news of the marketing boost earlier this week put BSkyB's shares in a tailspin sending them crashing 19% to 499p, wiping almost 100p off their value before they recovered some ground, rising above the 500p mark, to today's 511p.
The fall came despite BSkyB announcing profits had more than doubled for the year to June 30 to £514m, up from £253m last year, beating analyst expectations, while revenues climbed 15% to £3.7bn.
MediaCom confirmed the win but declined to comment further.
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