The jury deliberated for less than a day after a two-and-a-half week trial that told of briefcases bulging with cash and secret meetings involving Saddam Hussein and Boutros Boutros-Ghali, the former UN secretary-general.
US prosecutors said that Park Tongsun acted on behalf of Saddam by lobbying US and UN officials to drop economic sanctions, and broke the law by failing to notify the justice department.
They also said Park received about $2 million from Iraq and had asked for up to $10 million saying that he needed it to bribe his friend, Boutros-Ghali. There was no evidence Boutros-Ghali received any money.
Park, 71, faces up to five years in prison when he is sentenced on October 26.
Judge Denny Chin denied him bail, saying he was a flight risk, and Park has been held in a prison hospital to treat his diabetes.
"He is disappointed because he is not guilty. We are hoping Judge Chin will enter of judgment of acquittal," defence lawyer Michael Kim said.
Kim has asked for a dismissal, saying the conspiracy alleged could no longer be prosecuted under the statute of limitations.
Feisal Amin al-Istrabadi, Iraq's deputy UN ambassador, said Park's actions had strengthened the former government "and led to the continued oppression of the people of Iraq".
Widespread abuse of the $67 billion oil-for-food programme for personal gain has implicated officials, companies and politicians from 40 countries, according to a panel headed by Paul Volcker, a former US Federal Reserve chairman.
Six others under indictment over the scandal have yet to be tried, including Texas oil tycoon Oscar Wyatt.
Park previously had gained notoriety in the 1970s as a lobbyist who gave hundreds of thousands of dollars to members of the US Congress as part of the influence-peddling scandal dubbed "Koreagate". Charges against him were dropped.