Andrew Fastow, the former Enron finance executive, has been sentenced to six years in prison.
Andrew Fastow was sacked prior to Enron's 2001 collapse
The US energy giant went bankrupt in 2001 with debts of $31.8bn (£18bn).
Fastow, 44, had pleaded guilty to fraud and money laundering in 2004 and became the chief witness in the trial against Ken Lay and Jeffrey Skilling.
His testimony helped convict former chairman Mr Lay, who died in July, and former chief executive Skilling, who will be sentenced next month.
Fastow helped orchestrate a series of loss-making deals and financial schemes at Enron to hide debts from investors.
He admitted these actions were fraudulent and enabled him to steal money from the energy trading firm.
His jail term is four years less than the maximum provided by his 2004 plea agreement.
US District Judge Ken Hoyt said he had taken account of Fastow's cooperation with prosecutors, his desire to help victims suing to recover their losses, and his visible remorse.
The judge did not impose a fine, saying that Fastow has already forfeited more than $24m.
Fastow hugged his wife and surrendered immediately following the hearing.
His wife, Lea, has already served a year in prison after making her own plea bargain with prosecutors over the Enron affair.
Kirby Behre, a former federal prosecutor and an expert on sentencing, said Fastow had got off lightly.
"Andy Fastow, by any measure, should be the happiest guy on Earth today," he said.
"He was slated to get 10, could have gotten 20, and with any luck, he'll be out with five and change."