The two tied the knot at St. Mark's Church in Englefield, Berkshire in England Saturday in front of friends and family, including her sister Kate Middleton, her husband Prince William, their kids Prince George, 3, and Princess Charlotte, who served as a page boy and bridesmaid, and William's brother Prince Harry.
The ceremony space was decorated in gorgeous garlands of pink and white roses and other flowers.
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"It was a beautiful, traditional ceremony," a guest told E! News exclusively. Pippa and James both looked a little nervous but they were smiling at each other the entire ceremony. They were positively beaming. They kissed of course after exchanging vows! Their parents looked proud and there was an immense sense of joy in the air."
"They read their vows with absolute sincerity and, as expected, Pippa read more modern vows, not promising to 'obey' her husband," the guest continued. "That's quite normal these days."
The children, the person added, were "perfectly behaved inside," "although Charlotte began to cry at one point and [the kids' nanny] comforted her."
As predicted, Kate read a prayer, while the groom read "Love is an Adventure" by Pierre Teilhard de Chardin and his brother and best man Spencer Matthews read an excerpt from Paulo Coelho's novel The Alchemist.
Reverend Nick Wynne-Jones carried out the ceremony. The guest told E! News he "did a fantastic job."
"His sense of calm really brought a peaceful stillness to the church," they added. "You could hear birds chirping outside. It was beautiful."
Meanwhile, the choir of Winchester Cathedral lead Christian hymns during the service, including "Be Thou My Vision", "Tell Out, My Soul, The Greatness of Thy Lord", "I Vow Thee to My Country" and "Glorious Things of Thee Are Spoken."
After the ceremony, guests attended a Champagne reception at the private estate on which the church is located. They enjoyed sweet and savory canapés from pastry chef Fiona Cairns and Pippa and James' dads Michael Middleton and David Matthews gave short speeches.
The guests later headed to the wedding reception, held at Michael and wife Carole Middleton's home, about six miles away. Harry arrived with girlfriend Meghan Markle, after reportedly driving back to London, about 50 miles away, to pick her up.