Radel, a Florida Republican, is expected to issue a statement shortly, according to spokesman Greg Dolan.
Radel, 37, took office as a freshman in January 2013. On Oct. 29, he was arrested in a Washington, D.C. drug sting and charged with possessing cocaine, a misdemeanor offense.
He pleaded guilty to the charge in November and was sentenced to a year of probation and a $250 fine.
House Speaker John Boehner, R-Ohio, has shown a low tolerance for GOP members who get into trouble and he is known to privately encourage them to resign. Boehner did not publicly call on Radel to step down, but Republican leaders in Florida were more vocal and pushed for his resignation shortly after his arrest. Florida's 19th Congressional District, which Radel represents, leans Republican so it is unlikely his departure will give Democrats a chance to take over the seat in November.