Authorities say the freshman Republican was found in possession of cocaine on Oct. 29, a misdemeanor offense, but provided no other details.
NPR's Tamara Keith says the charge carries a statutory maximum sentence of 180 days of imprisonment and/or a fine of $1,000.
Radel, 37, represents Florida's 19th District, which covers parts of the Gulf Coast, Fort Myers and Naples.
He issued the following statement:
"I'm profoundly sorry to let down my family, particularly my wife and son, and the people of Southwest Florida. I struggle with the disease of alcoholism, and this led to an extremely irresponsible choice. As the father of a young son and a husband to a loving wife, I need to get help so I can be a better man for both of them.
"In facing this charge, I realize the disappointment my family, friends and constituents must feel. Believe me, I am disappointed in myself, and I stand ready to face the consequences of my actions.
"However, this unfortunate event does have a positive side. It offers me an opportunity to seek treatment and counseling. I know I have a problem and will do whatever is necessary to overcome it, hopefully setting an example for others struggling with this disease.
"During votes last Friday, Radel told a Washington Post reporter that the last few weeks of intense debate regarding the partisan government shutdown and new health-care law had been 'stressful' on his young family. Radel's wife, Amy, and their young child have been splitting their time between Washington and their Florida home so that the young family can be together more often.
"On Friday, Radel recounted how at the height of the 16-day shutdown, he had to drive his wife and child home to Florida because of an ear infection. He did not specify when the trip occurred."
"Radel is a former radio host, TV reporter and newspaper owner who was swept into office with Tea Party support. He was born and raised in Cincinnati, where his family owned a funeral home company.
"A spokesman for House Speaker John Boehner said the incident is 'between Rep. Radel, his family and his constituents.'
" 'Members of Congress should be held to the highest standards and the alleged crime will be handled by the courts,' Boehner spokesman Michael Steel said."
Update at 8:20 p.m. ET. Radel Reportedly Bought Cocaine From Undercover Officer:
The Associated Press reports:
"A Drug Enforcement Administration official said Radel allegedly bought cocaine from an undercover agent in Washington's Dupont Circle neighborhood on Oct. 29. Later that night, federal authorities went to his apartment and informed him that he would be facing criminal charges related to his purchase of cocaine.
The official, who spoke on the condition of anonymity because he was not authorized to release details of the case in his own name, said Radel was identified to authorities as a cocaine buyer by his suspected dealer. The dealer had been previously arrested as part of a separate drug investigation led by a federal task force.
DEA spokeswoman Barbara Carreno confirmed that the charge resulted from a joint DEA-FBI investigation."