Shona Seifert and Thomas Early now face sentencing on May 16 and could be looking at up to five years in prison, as well as a fine.
They were found guilty by a jury in New York of 10 charges, including making false claims and conspiracy. The jury deliberated for under six hours and the guilty verdict was unanimous.
The case concerned Ogilvy & Mather's work on the US government's Office of National Drug Control Policy in 1999 and 2000.
Seifert and Early staunchly denied charges that they had told staff to falsify time sheets and inflate the number of hours they had worked on the account after discovering that the agency had billed the government $3m less than anticipated.
However, the prosecution supplied evidence in the form of email messages, including one in which Seifert vowed: "I'll wring the money out of them. I promise".
They had also used handwriting analysis on timesheets, which indicated that Seifert had ordered a shift in billings from other accounts to the ONDCP account.
But the prosecution's biggest weapon was evidence from two other former employees who had already pleaded guilty. Ogilvy & Mather was not involved in the case after settling with the government in a $1.8m payout.
Seifert left Ogilvy & Mather in 2002 to become president of the New York office of TBWA\Chiat\Day, but the agency has since brought in Brett Gosper to take on that role, and her future at the agency is unclear.
Early resigned from his role of chief financial officer at Ogilvy & Mather New York after being charged last year. Both will remain free on bail until sentencing in May.
The $130m (拢70m) account moved to Interpublic Group's Foote Cone & Belding in 2004.
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