Cunningham, 63, entered pleas in U.S. District Court to charges of conspiracy to commit bribery, mail fraud and wire fraud, and tax evasion for underreporting his income in 2004.
He could receive a maximum sentence of 10 years in prison.
The eight-term Republican congressman answered "yes, Your Honor" when asked by U.S. District Judge Larry Burns if he had accepted bribes from someone in exchange for his performance of official duties.
Read the charges against Rep. Randy Cunningham and the plea agreement.
After the hearing, Cunningham was taken away for fingerprinting. He was released on his own recognizance until a Feb. 27 sentencing hearing.
He also agreed to forfeit to the government his Rancho Santa Fe home, more than $1.8 million in cash and antiques and rugs.
Cunningham, who had been in Congress since 1991, had already announced in July that he would not seek re-election next year.
The former Vietnam War flying ace is known on Capitol Hill for his interest in defense issues and his occasional temperamental outbursts.
He drew little notice outside his San Diego-area district before the San Diego Union-Tribune reported last June that he'd sold the home to Wade.
"He is definitely going to get some prison time," says CBS News legal analyst Andrew Cohen, "although I suspect he won't get close to the 10-year maximum he faces. Prosecutors already have made an example of him and will ask the judge to do so as well and I don't see a whole lot on Cunningham's side of the equation to suggest a ton of leniency. "
As to why prosecutors didn't file actual bribery charges against Cunningham, Cohen says "It's the Al Capone theory of federal prosecution. You don't necessarily get the guy for the underlying crime you get him for tax evasion, and mail and wire fraud, and conspiracy – all of the satellite charges that surround a case like this and certainly have a lot of bite when it comes to prison time."
In a statement, prosecutors said Cunningham admitted to receiving at least $2.4 million in bribes paid to him by several conspirators through a variety of methods, including checks totaling over $1 million, cash, rugs, antiques, furniture, yacht club fees and vacations.
"He did the worst thing an elected official can do — he enriched himself through his position and violated the trust of those who put him there," U.S. Attorney Carol Lam said. The statement did not identify the conspirators.
The case began when authorities started investigating whether Cunningham and his wife, Nancy, used the proceeds from the $1,675,000 sale to defense contractor Mitchell Wade to buy a $2.55 million mansion in ritzy Rancho Santa Fe. Wade put the Del Mar house back on the market and sold it after nearly a year for $975,000 — a loss of $700,000.
(CBS News correspondent Jim Stewart reported on the Cunningham case in July. See video of the congressman's former home and the yacht where he lives in Washington.)
Cunningham's pleas came amid a series of GOP scandals. Rep. Tom DeLay of Texas had to step down as majority leader after he was indicted in a campaign finance case; a stock sale by Senate Majority Leader Bill Frist is being looked at by regulators; and Vice President Dick Cheney's chief of staff was indicted in the CIA leak case.