Duchess of Cambridge Kate Middleton wore J Brand 811 jeans for her trip to Mustique on Jan. 25. Credit: Bauer-Griffin

The Duchess does denim!

For her first overseas vacation with son Prince George, Kate Middleton chose a cool-but-casual outfit: a striped shirt and her go-to jeans. 

In fact, the chic combo isn't the first time the Duchess, 32, has chosen the flattering look. Wearing the white-and-navy striped Ralph Lauren top with her navy J Brand 811 jeans has been a go-to for Middleton when she ditches the designer gowns but still wants to look pulled together.

In October 2013, she wore the combo to a SportsAid event, just three months after giving birth. And in July 2012, Middleton wore the J Brand jeans with a similar striped shirt to the London Olympics.

Unlike her Alexander McQueens and Jenny Packham dresses, the $169 mid-rise, skinny jeans are actually affordable.

Middleton joined dad Michael Middleton, brother James, and sister Pippa in Mustique to celebrate mom Carole's 59th birthday. Prince William stayed behind for University of Cambridge classes.