Still, the former OC actress can be forgiven for her sartorial slip-up this time - she was in character, playing a pregnant prostitute.
The 23-year-old was caught by photographers mid-way through filming scenes for the American TV series Law and Order: SVU in New York's Meatpacking district.
Ready for my close-up: Mischa Barton lets it all hang out on location as she films Law & Order: SVU in New York
Down and out in New York: Mischa gets into character
Hollywood heavyweight Sharon Stone has also been roped in for a cameo appearance on the show.
While Mischa will play a hooker called Gladys, Sharon will play an ex-cop turned prosecutor over four episodes.
According to programme sources, Mischa turns to Detective Benson, played by Mariska Hargitay, for help in a life-or-death decision.
Her decision to appear in the TV show appears to be something of a u-turn for Mischa, who had vowed to pursue 'more serious roles'.
Make me up: Mischa sucked on a lollipop as a make-up artist applied a red injury mark on her a neck
Just four months ago she said: 'I think I need to back away from the whole TV approach.
'That whole world of network television probably isn't, for me, a good idea now. I need to start reading for more serious roles.
'I want to go fighting for interesting things and look for something that's going to be interesting for me.'
Sitting not-so-pretty: Mischa sucks on a lollipop in her role as hooker 'Gladys'
No cop-out: Mischa takes a picture of herself - including her neck 'injury' - with a real-life policeman on the set of Law and Order
Her declaration came shortly after the cancellation of her latest series, The Beautiful Life.
The show, which was produced by Demi Moore's husband Ashton Kutcher, was dropped in September after just two episodes due to poor ratings.
Mischa's episode of Law and Order: Special Victims Unit will air on NBC on March 3
Down time: Mischa swapped her character's tacky heels for a pair of comfy Ugg boots in between scenes