PIC: See Pippa Middleton's Stunning Evening Gown

Credit: Splash News Online

Brilliant Bridesmaid! 

It was Kate Middleton's big day, but all eyes were on her baby sis Pippa that night, when the maid of honor, 27, donned a stunning emerald green gown with Aruna Seth's silver "Lynn" heels ($875, arunaseth.com) for the evening wedding reception at Buckingham Palace.

The sexy dress was custom designed by Temperley, the design house confirms to Us Weekly. 

PHOTOS: Highlights of the royal wedding

Hopefully Pippa was still able to cut a rug in the sexy sheath; the lavish party, thrown by Prince Charles for 300 lucky guests, included dinner and dancing.

Commemorate Will & Kate's big day with our Us Collectors Edition: Royal Wedding with photos and details from the wedding. Available for pre-order now and on sale May 6.