But the judge agreed to delay sentencing until April 13.
Mowen had been facing six charges in federal court, including wire fraud, soliciting murder of witnesses, tampering with a witness and retaliating against a witness.
Prosecutor Mark Hirata said Mowen took in about $18 million but used about half of that as Ponzi payments in which money from new investors is paid to older ones, a scheme to make a business appear profitable when it is not. Mowen had promised investors a return of up to 33 percent a month by trading in foreign currency and investing in real estate.
Mowen fled the United States in the fall of 2008 when confronted by investors. He was arrested in Panama in April 2009 after the indictment against him was unsealed and authorities were tipped to his whereabouts.
Mowen has been held since his arrest in the Davis County Jail. He told Benson part of his reluctance to be sentenced Thursday was because he would be moved to a different part of the jail until he is transported to federal prison and did not want that.
While in the jail, he allegedly approached an inmate about killing four witnesses in the case.
U.S. Attorney Carlie Christensen said the government agreed to drop the solicitation of murder counts "for the greater good" and because investors will get back about $3 million of their money sooner. The charge Mowen pleaded guilty to also reflected the crimes he committed, she said.
"We believe it was representative of the criminal conduct he was charged with," Christensen said outside the federal courthouse in Salt Lake City after sitting through the hearing.
James McTighe, special agent in charge of the FBI's Salt Lake City division, said after the court session the plea should serve as a warning to investors in Utah who have been plagued in recent years by a wave of financial fraud.
"I think it's a message to the public to be aware," he said.
Mowen's attorney, Stephen McCaughey, asked Benson to recommend that Mowen be sent to the Terminal Island federal prison in the Los Angeles area and be treated for alcoholism.
Mowen, 48, was previously convicted of securities fraud in Utah in 2003, 2004 and 2007. He also had theft convictions in 2003 and 2004, according to court records.
Mowen had used about $6 million of investor monies to purchase 200 high-end antique, classic and muscle vehicles, including cars, trucks, trailers, motorcycles and three-wheelers, most of which were auctioned off last year.
The guilty plea means another two dozen or so vehicles will be sold, and Mowen also agreed to forfeit a home in Lindon, $495,912 plus interest in an annuity and other property.