Pippa Middleton is definitely in wedding shape!

The 33-year-old showed off her toned arms in a chic, sleeveless gown just weeks before her wedding to James Matthews.

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Middleton looked stunning in her elegant Erdem dress at the ParaSnowBall fundraiser at the Hurlingham Club in London Thursday, accessorizing her look with minimal jewelry and a simple clutch. The brunette beauty has been an avid supporter of the charity sponsoring the event, Disability Snowsport UK.

Middleton, who is set to marry Matthews on May 20 at St. Mark's Church in Englefield, England, made her first public appearance with her fiance at the event.

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A source told ET  last month that in addition to hair treatments at her favorite salon, Richard Ward, Middleton has been preparing for her wedding with extra time in the gym.

"Pippa has been stepping up her workouts getting ready for her wedding," the source revealed. "She's been working out about four or five times a week."

"She's been working with a personal trainer at a gym near her home in Chelsea and also has been doing Pilates," the source continued. "She looks and feels great -- she's never looked better."

See more in the video below.