The business is estimated to be worth as much as $90m (拢56.5m), although the company spent far less than this on advertising last year.
IBM announced it was to buy the accounting firm on August 1 in a $3.5bn deal, which significantly boosts its professional services business. It has since been reported that the computer giant plans to cut as many as 4,000 jobs following the takeover.
Ogilvy & Mather has held IBM's global advertising and marketing business for a number of years, winning its global advertising business first in 1994.
Last year, IBM dropped Havas's US agency, Brann Worldwide, from its direct marketing business in a move that saw the company consolidating its global direct and interactive marketing strategies through WPP.
IBM pooled its business into the New York offices of WPP Group's OgilvyOne and Wunderman.
OgilvyOne already adapts the US work for the UK market, as well as producing some original work. The centralisation is expected to see a rise in output from the UK office.
The PwC account had previously been split between the Interpublic Group of Companies-owned Hill, Holliday, Connors, Cosmopulos and McCann-Erickson Worldwide.
Earlier this week, it was reported that Cisco Systems, the networking company, had awarded Ogilvy a $200m branding campaign.
Cisco's business was being run by darkGrey, a San Francisco-based unit of Grey Global Group.
However, the recent arrival of a former IBM marketing executive has seen Ogilvy & Mather step into run the new campaign. The status of the Grey-owned agency on the account is now unclear.
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