And the dress? Well, from the front we weren't bowled over. The shape is a little boxy and, dare we say, even ageing on the 23-year-old.
But the magic was all happening at the back as the young star turned to show off the beautiful draping and her amazing figure.
J-Law's white silk dress was by Dior, and she teamed it with heels from Kurt Geiger London Collection.
She was joined on the red carpet by her handsome co-stars Liam Hemsworth and Josh Hutchinson (who's a lot smaller than we realised btw).
See more of Jen's elegant style below: