Sienna Miller puts on a leggy display in a green suede mini dress as she joins her boyfriend Oli Green for Anna Wintour’s pre-Met Gala dinner in NYC

She welcomed her second child four months ago.

And Sienna Miller proudly showed off her post-baby figure as she headed to Anna Wintour’s pre-Met Gala dinner with her boyfriend Oli Green on Sunday night.

The actress, 42, showed off her endless pins in a green suede mini dress as she headed to the party at Anna’s chic apartment in the Big Apple.

Sienna’s little dress was decorated with oversized white lily details, and she wore sheer tights and white pointed-toe heels.

Sienna was among a slew of big names who arrived at Anna’s apartment for the occasion, with stars including Zendaya and Jennifer Lopez also appearing.

Sienna Miller proudly showed off her post-baby figure in a green mini dress as she attended Anna Wintour’s pre-Met Gala dinner with boyfriend Oli Green on Sunday evening

The actress showed off her endless pins in a green suede mini dress as she headed to the party at Anna's chic apartment in the Big Apple

The actress showed off her endless pins in a green suede mini dress as she headed to the party at Anna’s chic apartment in the Big Apple

Sienna's little dress had white bow details, and she accessorized with sheer tights and white pointed-toe heels

Sienna’s little dress had white bow detailing, and she accessorized with sheer tights and white pointed-toe heels

She and her boyfriend Oli welcomed their first child together, a girl, in January. Sienna also has a daughter Marlowe, 10.

The Costume Institute’s Spring Exhibition falls on the first Monday in May each year and is held at the Metropolitan Museum of Art in New York City.

This year the event is called Sleeping Beauties: Reawakening Fashion, while the dress code is The Garden of Time.

The chairs of honor for the evening are Loewe creative director Jonathan Anderson and TikTok CEO Shou Zi Chew.

“This year’s co-chairs reflect a variety of career achievements and each has their own style history at the Met Gala,” Vogue said.

The display will feature approximately 250 items from The Costume Institute’s permanent collection. Many of the pieces are too fragile to ever be worn again.

The pieces are all rendered using elements such as AI, GCI and more, while themes such as land, sea and sky are played out.

“It is very much an ode to nature and the emotional poetics of fashion,” says Andrew Bolton, Wendy Yu Curator responsible for The Costume Institute, about the upcoming exhibition.

It comes just four months after Sienna welcomed her second child

She stunned in the striking green mini dress

Just four months after welcoming her second child, Sienna stunned in the striking green mini dress

The actress's glamorous look comes as the fashion world counts down to the star-studded Met Gala, which takes place on Monday evening

The actress’s glamorous look comes as the fashion world counts down to the star-studded Met Gala, which takes place on Monday evening

Sienna beamed as she arrived for Anna's annual pre-party with her boyfriend in tow

Sienna beamed as she arrived for Anna’s annual pre-party with her boyfriend in tow

She and her boyfriend Oli welcomed their first child together, a girl, in January.  Sienna also has a daughter Marlowe, 10

She and her boyfriend Oli welcomed their first child together, a girl, in January. Sienna also has a daughter Marlowe, 10

The Costume Institute's Spring Exhibition falls on the first Monday in May each year and is held at the Metropolitan Museum of Art in New York City

The Costume Institute’s Spring Exhibition falls on the first Monday in May each year and is held at the Metropolitan Museum of Art in New York City

This year the event is called Sleeping Beauties: Reawakening Fashion, while the dress code is The Garden of Time

This year the event is called Sleeping Beauties: Reawakening Fashion, while the dress code is The Garden of Time

“One thing I hope this show will activate is the sensory appreciation of fashion.”

Guests expected to attend include the Kardashians, Blake Lively, Hailey Bieber, Sarah Jessica Parker and Timothee Chalamet.

Gwendoline Christie, La La Anthony and Ashley Graham will host, while YouTuber Emma Chamberlain is expected to interview stars on the red carpet.

Last year’s gala honored the late designer Karl Lagerfeld.