Sienna Miller’s Casual Chic Style

This month, Sienna Miller launched her latest Twenty8Twelve collection with her sister Savannah for the UK-based department store Selfridges. The line's relaxed, understated look in muted shades of grey with occasional splashes of warm color perfectly reflects Sienna's casual-but-chic personal style. At the launch, Sienna wore head-to-toe Twenty8Twelve. Her daring platform leather booties added an edgy touch of sophistication to her heather-gray boatneck sweater, shorts, and tights.

Sienna and Savannah Miller at their clothing launch in London.Sienna Miller wearing a grey sweater and red boots.

Like any great fashionista, Sienna knows how to re-work her staples; here she is, wearing the same sweater with black jeans and red boots at the Groucho Club in Soho for a more casual, fun look.

Sienna Miller wearing a furry white jacket.Sienna Miller wearing a furry white jacket with a dress.

Sienna loves her furry white jacket, which she wore in true rocker fashion with acid-washed denim and a graphic tee as she left the Theatre Royal Haymarket in London, where she's currently performing in the play Flare Path. The jacket also worked brilliantly dressed up with tights and a silk floral dress.

Sienna Miller wears a slouchy sweater.Sienna Miller wears a knit sweater and blazer.

Sienna is the queen of the slouchy sweater, an essential for transitioning to the warmer weather of spring. Take a cue from Sienna, and cuff the sleeves of an oversized sweater, like she did with this red and white striped one; or, you can layer a thinner knit with a t-shirt and blazer, to imitate the casually put-together look she wore to a pub in the West End.