Kate Middleton Rocks Casual Stripes to Greet London Marathon Runners -- See Her Laid-Back Look!

Getty Images

The Duchess of Cambridge traded in her dresses and heels for a simple sweater and tennis shoes on Wednesday.

Kate Middleton goes casual!

The Duchess of Cambridge, who normally sports chic dresses and trendy coats, opted for a more laid-back ensemble while greeting the #TeamHeadsTogether runners at Kensington Palace on Wednesday, ahead of the 2017 Virginia Money London Marathon.

WATCH: Kate Middleton Stuns in Alexander McQueen at Paris Gala

Middleton wore a white Luisa Spagoli Muvi sweater with red and black horizontal stripes ($280), which she paired with skinny jeans and white Superga tennis shoes ($65).

Getty Images

Though her outfit was more on the comfy side, her beauty look made up for it! She kept her brunette tresses down with a slight curl at the ends, and rocked a light pink pout and a touch of rosy blush.

Getty Images

Middleton was all smiles while chatting with some of the runners, who are in their final preparations for the big race on Sunday.

According to a post on Kensington Palace's official Instagram page, around 70 Royal Mail post-boxes "will be wrapped with @heads_together headbands on the @LondonMarathon route."

Meanwhile, Prince Harry opened the London Marathon Exposition with help from a 5-year-old girl, Melissa, who did the honors of cutting the red-and-white ribbon.

He also left a special message to the #TeamHeadsTogether runners on a whiteboard, which read, "Good luck guys! Smash it!"

WATCH: Kate Middleton Curtsies to the Queen in Perfect Easter Ensemble: Pics!

Over the weekend, Middleton went all out for her Easter Sunday look, chic in a high-collared ivory Catherine Walker dresscoat with a matching pillbox hat and heels.

Hear more on the ultra-classy ensemble (and see the pics!) in the video below.