Maurice Cloutier entered the plea in court in Moncton on Tuesday morning. A charge of forcible confinement was dropped.
Cloutier was initially charged with aggravated sexual assault and forcible confinement following the incident on April 25 in Moncton.
Witnesses called 911 after they saw a young woman running naked through a parking lot near the intersection of Church Street and Mountain Road.
Police say the woman was escaping from a transport truck and screaming for help. The transport truck left the scene before police could stop it.
Cloutier was located by Quebec police on Wednesday. His truck was searched and he was arrested.
Cloutier will be back in court for sentencing on June 24.