Michael, 43, said in Brent Magistrates Court that he was guilty due to "tiredness and prescribed drugs."
The pop star, whose birth name is George Panayiotou, was arrested on Oct. 2 in London.
A charge of being in charge of a vehicle while unfit through drugs was dropped by the Crown Prosecution Service. Sentencing was to be passed at a later date.
Michael was arrested in the early hours of Oct. 2 after police responded to complaints that a car was blocking an intersection in North London. Police said he was found slumped over the wheel of the car.