Sienna Miller Twists Her Business-Casual Look From Mango Into Fall's Cool-Girl Uniform

When celebrities reach A-list status, they don't just swear off their most beloved mall brands. Selena Gomez still shops at Zara, Hailey Bieber remains a loyal Gap girl, and, on September 15, Sienna Miller sported Mango styles on her press tour for War. No surprise there: She's been stocking her business-casual work wardrobe with the Spanish brand for years.

Two weeks before the legal drama series debuts on HBO and just in time for London Fashion Week, Miller returned to London's street style circuit. Paparazzi spotted the local cool-girl in a baby blue button-down, a tailored black coat, and wool barrel-leg trousers, all from Mango Selection, the brand's high-end clothing collection. The actor's Straight Poplin Shirt sold out soon after she put the day-to-night staple on everyone's radar. Not only is an almost identical Oxford shirt available for under $50, but her overcoat and bottoms are still up for grabs, too.

If anyone on Team Marie Claire was feeling in-office fashion fatigue, Miller solved our problem by presenting the ultimate corporate-chic uniform for fall. All she needed was a laptop bag on her shoulder and loafers on her feet to really sell the "I'm serving looks from 9-to-5" bit.

Instead, to prove the wrong shoe theory right, the A-lister styled strappy tomato-red stilettos. Unexpected shoe pairings are a classic Sienna Miller move, though. Last month, she styled a boho-chic button-down and flared '70s jeans with the high-vamp flats trend, giving the nostalgic pieces a modern makeover.

For her finishing touches, Miller accessorized with oval sunglasses, a gold chainlink necklace from Monica Vinader, and matching rings, also by the London-based brand that, like Mango, has stayed in her closet for years. (She wore a friendship bracelet by Monica Vinader as early as Coachella in 2014.)

Mango and Miller have a history, dating back to the 2020 Sundance Film Festival, the Glastonbury Festival in 2022, and plenty of vacations to St. Tropez and Paris over the years. Similar to Kaia Gerber, Katie Holmes, and Alexa Chung, the Horizon star is especially fond of the brand's outerwear.

Back in March 2024, she wore another relaxed professional set—featuring a butter yellow cardigan and khaki pants—with a single-breasted, charcoal gray coat from Mango. Two months later, she endorsed the label's collaboration with Victoria Beckham, sporting a classic beige trench coat around London.

If this Mango look is anything like her previous picks, Miller's endorsement could make it impossible to track down soon. The shirt is already sold out, so time is of the essence. But don't worry, when her fans inevitably snatch the last sizes of her coat and trousers, shop the similar styles below.

Shop Business-Casual Looks Inspired by Sienna Miller in Mango