
Hearst, which owns UK-based The National Magazine Company, has spent several months unsuccessfully courting iCrossing. The media group originally approached iCrossing with an unsolicited bid of $250m, which was rejected.
Following the rebuffal, iCrossing hired Bank of America to help it attract higher offers. This led to approaches from WPP, Dentsu and Aegis.
But iCrossing has agreed to Hearst's latest offer, and the deal is expected to be completed within the next few weeks, subject to regulatory approval.
Don Scales, iCrossing's US-based chief executive, will remain in his post, although iCrossing's board will depart. The deal will not affect the jobs of iCrossing's 125 UK staff.
Doleman confirmed that there would be no redundancies in the UK. He said that, on the contrary, Hearst would "aggressively invest" in the agency.
He added that the relationship would enable iCrossing UK to tap into Hearst's and Natmag's magazine data and use it for clients; and conversely use its own digital marketing expertise to improve Hearst's online strategy.
The deal will enable Hearst to tap into iCrossing's expertise in search marketing and online brand tracking. The media firm has set up a new division called Hearst Marketing Services, which will be headed up by Hearst Magazines senior vice president Matthew Petersen and will oversee iCrossing.
Frank Bennack, Hearst's chief executive, said that iCrossing would still operate as a separate business but added it could provide "tutoring" for Hearst's TV and magazine properties.
He said: "Search and online marketing expertise will be an important asset for us as we continue to look for new ways to reach key audiences through digital marketing for our brands and our clients."
US-based iCrossing has offices across the globe, including in London, Brighton and Munich. Its presence in the US spans Dallas, Los Angeles, New York and San Francisco. The business was founded in Arizona in 1998.
Hearst owns consumer magazines including Cosmopolitan, Esquire and Harper's Bazaar.
The deal comes three years .
Last month, .