U.S. District Judge Kenneth Hoyt sentenced Ben Glisan to five years in prison on a conspiracy charge, the maximum term allowed.
Prosecutors said there was no deal to implicate higher-ranking executives such as Enron's former chairman Kenneth Lay and former chief executive Jeffrey Skilling.
Glisan, 37, also agreed to forfeit nearly $1 million in profits from a partnership investment related to Enron and agreed to not seek a refund of $412,000 in income taxes he paid on that profit.
"I think I would simply like to say I take full responsibility for my actions," Glisan told the judge.
Twenty-three other counts against Glisan were dismissed. Glisan was taken into custody immediately.
Glisan had earlier pleading innocent to charges of money laundering, wire fraud and conspiracy as part of a 109-count indictment against his one-time boss, former Enron finance chief Andrew Fastow.
He was the second former Enron executive to plead guilty in the scandal. Michael Kopper, once one of Fastow's top lieutenants, pleaded guilty in August 2002 to money laundering and conspiracy.
Glisan was fired in November 2001, less than a month before Enron filed for bankruptcy, when an internal probe revealed he gained $1 million from a $5,800 investment in one of several complex deals at the heart of the Justice Department's case against the Houston company.
Early last year, Glisan and his legal team tried to strike a deal with the Justice Department and avoid prosecution by telling what he knows about the financial details.
On May 1, prosecutors filed a superseding indictment that expanded the 78-count indictment against Fastow to the 109 counts to include Glisan, among others. Glisan joins Michael Kopper, once one of Fastow's top lieutenants, who pleaded guilty in August 2002 to money laundering and conspiracy.
Robert Mintz, a former federal prosecutor with McCarter & English in Newark, N.J., said Glisan could offer prosecutors another major weapon in their arsenal against Fastow.
Glisan's value lies in how he can further the Justice Department's case, Mintz said. "They're going to want more than they already have," he said.
However, Leslie Caldwell, chief of the task force investigating the Enron case, said authorities did not offer Glisan a better deal for cooperation.
"We are fully prepared to go forward against Mr. Fastow without Mr. Glisan," she said.
"We have witnesses and we're getting more witnesses and Mr. Glisan is not one of them."
Just last week, Hoyt ruled that Fastow would be tried separately from his co-defendants, setting Fastow's trial for April 20, Glisan's for July 20 and former finance executive Dan Boyle's for Aug. 17.
Hoyt said the trials were split partially because of the discrepancy in the number of counts against Fastow in comparison to his co-defendants, "as well as the impact that such evidence may have on a jury."
Boyle has pleaded innocent to two counts of conspiracy.
Fastow has pleaded innocent to fraud, money laundering, insider trading and other charges for allegedly masterminding schemes and partnerships to enrich himself, his family and friends at the expense of Enron and its investors.
Prosecutors have frozen about $23 million held in bank and brokerage accounts by Fastow, his family and others. Of those, more than $900,000 is in an account in the names of Glisan and his wife, Barbara.
In December, Glisan said in court documents that he declared the $1 million profit from his partnership investment as income and paid $412,000 in taxes. He offered to turn over the remaining $628,744 to prosecutors, but that and the other forfeiture cases have been put on hold until the criminal prosecutions have concluded.
Kopper said in court papers he helped Fastow run shady partnerships that lined their pockets with millions at the expense of the company.
Kopper quit Enron in July 2001 to run one of those partnerships. As part of his plea agreement, he surrendered $11.8 million in ill-gotten gains.