The 37-year-old was out in North London with her husband of three years, Sacha Baron Cohen, when she was seen getting out of the family car alongside her two daughters, Olive, five, and Elula, two, on Saturday.
But as she helped her children out of their white car the wind blew the Australian actress's skirt up and flashed her tiny, pert bottom in a pair of grey knickers.
Flashing: Isla Fisher was spotted out with husband Sacha Baron Cohen in North London but had trouble keeping her skirt at bay
Her infamous red hair was plaited to one side in a loose pigtail and finished off the outfit with a pair of drop earrings, and black Roman sandals.
Isla, who was born to Scottish parents, born in Oman but raised in Perth, has been hot on the film scene recently having starred as Myrtle Wilson in Baz Luhrmann's The Great Gatsby and Henley Reeves in Now You See Me.
Exposed: Isla Fisher did her best to keep her skirt down but still unintentionally exposed her pert bottom
She said: 'Family is 100 per cent my top priority.
'So I’m much more comfortable doing supporting roles right now.
'And often they’re the most interesting. You get to be a character actress.'
Stylish: Isla looked effortlessly stylish in a paisley dress and sleeveless denim jacket as she stepped out in North London
Isla meet Sacha in Sydney in 2002 and married in Paris in 2010 also converted to Judaism and took the Hebrew name Ayala, meaning doe.
Sacha, who went to Haberdashers' Aske's Boys' School, just North of London, looked almost unrecognisable in a navy blue flat cap, large spectacles, a pale blue T-shirt and grey trousers.
The look was a far cry from his alter-ego, Ali G, Borat or Bruno, but with a flecks of grey in his beard it appears the 41-year-old is fitting into his role as supportive father.
Juggler: The Australian actress helped her little girl out of the car (right) whilst carrying a coffee cup and blue balloon at the same time
Helping hand: Isla helped her children out of the car as she and husband Sacha Baron Cohen went on a day trip in North London