Jerome Jacobson, 59, pleaded guilty to conspiracy and mail fraud for masterminding the theft of $24 million in winning game pieces, some worth up to $1 million each, from a McDonald's game promotion.
He agreed to repay $12.4 million and faces up to 15 years in prison.
Simon Marketing's parent, Simon Worlwide, last month revealed it expects to sell off its holdings, possibly through bankruptcy. Simon also has been informed by Nasdaq that its stock will be delisted on May 15.
Simon said it doubted its ability to continue operating and said it would cut its worldwide workforce to 46 by the end of the first quarter.
The company lost its two biggest clients, McDonld's and Philip Morris Cos., following Mr. Jacobson's arrest.