He and Meghan were then reportedly given a private suite before Harry made his way to the wedding ceremony at St Mark's Church with his brother Prince William.
She wore a custom wedding gown designed by Giles Deacon, a long veil by prominent hat-maker Stephen Jones, and a sparkly tiara.
ET can confirm that the Suits star was in attendance for Pippa Middleton's wedding reception held at the Middleton family estate in Bucklebury, England, on Saturday. The couple, who began dating last summer, joined almost 300 other guests at the evening receptio. Deacon said the lace bodice was embroidered with pearl details over a layered organza-and-tulle underskirt.
Kate, so often the centre of attention as she performs her royal duties or poses for the cover of Vogue, gracefully ceded the spotlight to her younger sister. In addition to Duchess Kate, Prince George and Princess Charlotte served as members of the wedding party.
William Hill spokesman Rupert Adams said: "Harry would not have wanted to rain on Pippa's parade by getting engaged before her big day".
Matthew and Pippa briefly dated in 2012 but became serious a year ago. Other guests included Roger Federer, his wife Mirka and Princess Eugenie. The Duchess of Cambridge wore a long-sleeved, blush pink Alexander McQueen dress.
"As I have found out, recognition has its upside, its downside and - you may say - its backside", Pippa later joked, according to People, adding that her infamous dress "fitted a little too well".
The duchess arrived with the young group, who wore outfits by exclusive children's clothing company Pepa & Co, and marshalled them back into the two luxury limousines that ferried them to the church.
The airspace above both villages was closed to prevent intrusive press crews from flying overhead or launching drones to get video footage.
There is some speculation that Harry will bring his American girlfriend, actress Meghan Markle, to the reception.
She has written a book about entertaining and columns for Vanity Fair while also working at her parents' lucrative "Party Pieces" business.