Armstrong hit two parked cars in Aspen, and initially his girlfriend Anna Hansen took the blame for the incident; however it later came out that the seven-times Tour de France winner was the driver of the car.
According to AP, Armstrong entered his plea by mail. He also paid $238.50 to cover court fees and a $150 fine.
Reports have claimed that Hansen told police, "We've had our family name smeared over every paper in the world in the last couple of years and honestly, I've got teenagers, I just wanted to protect my family."
Just two days ago it was revealed that Armstrong, who was stripped of all his Tour de France victories due to the use of banned substances, was ordered to pay $US 10 million to SCA promotions. The Texan is also being sued by his former teammate Floyd Landis and the US federal government.