He responded "guilty" to a single charge of driving while over the limit.
Inside the court, as she handed down her sentence, District Judge told McPartlin: "You were a man of good character...you have lost that good character".
As Ant faced his verdict at Wimbledon Magistrates Court on Monday, it emerged that he was twice the legal limit when he crashed with his mum Christine Woodhall in the vehicle. I've let myself down, I let a lot of people down. For that I'm truly sorry'.
The court ordered him to pay a fine of £86,000, which works out as around 4.5 days wages for the presenter.
The driver of the other Mini vehicle also told the court they thought they could have died in the incident.
Wearing a black, three-piece suit, white shirt and black tie, McPartlin stood in the glass dock in court, sporting a light beard.
In a letter read out in court, the telly star was full of remorse, as he admitted: 'I'm very sorry I did this.
"I am ashamed and mortified this happened".
On 21 March he was charged with drink driving following his involvement in a three-car smash on 18 March, where he allegedly failed a roadside breathalyser.
Meanwhile a witness statement from a driver of one of the two cars involved in the collision with McPartlin said that he and his wife "could have died as a result of Mr McPartlin's reckless driving".
When he was breathalysed by police he was found to have 75mcg of alcohol per 100ml of breath - the legal limit is 35 mcg.