Harrisburg police said Rep. John T. Galloway, 50, refused to submit to a breath test, and told investigators he was coming from the Capitol Complex at the time.
Capt. Annette Oates said Galloway was alone in the car and that he failed field-sobriety tests. She said he was released after sobering up.
Oates said a summons was being mailed to the Bucks County Democrat's home in Levittown.
He also is being charged with not using his turn signals and failure to stop at a stop sign, she said.
Galloway, 50, did not return an email or several messages left at his office and home.
A spokesman for the House Democratic caucus, Bill Patton, said he had few details about the incident and that Galloway had been placed on legislative leave Tuesday. Patton said the vehicle Galloway was driving is not state-owned.
Galloway is currently serving his third term in the House, having been first elected in 2006.