Mischa, who starred as Marisa in hit TV show The OC, took to the red carpet at the 8th Annual BritWeek Launch Party in a flowing black and white printed maxi dress.
And the frock featured a plunging neckline that exposed not just her cleavage, but most of her stomach too. Oo-err!
Luckily, Mischa's dress had a sheer nude mesh panel, so she was in no danger of falling out of it. Phew! We're all in favour of a plunging neckline, but surely the point of a floaty maxi dress is that you don't have to hold your stomach in?!
The sheer chiffon maxi featured cuffed sleeves for a 70s feel, and Mischa also wore a silver, gold and black multi-strand necklace, featuring star and moon charms, adding to the 70s-inspired look.
Meanwhile, Mischa recently debuted a new long bob ahead of her role in upcoming movie, The Hoarder, in which she stars alongside Inbetweeners actress, Emily Atack.
We're loving long floaty maxi dresses for festival season - but we're nowhere near as daring as Mischa, so we'll be layering ours over a vest top!
What do you think of Mischa's dress, fashion hit or miss? Let us know in the comments box below - our favourite comment from across the site each week wins £50!