In a poignant moment, as William stared forward waiting for his bride to walk down the aisle, he nervously chewed on his lip, a reminder of Diana's own habit.
The bride's sheer veil, worn down for the ride to the ceremony, was reminiscent of Diana's, although the classic lace-bodice gown, designed by Alexander McQueen's Sarah Burton, was more understated than Diana's with its 25-foot train.
And both Middleton and the late princess decided to take the word "obey" out of their vows, pledging, rather to "love him, comfort him, honor and keep him."
Middleton now wears the stunning diamond and sapphire engagement ring that Prince Charles gave to then Lady Diana as she traveled the same route that William walked, his head down as a 15-year-old, behind his mother's coffin.
William has spoken of his close relationship with his mother, who died at 36 in a Paris car crash, and he had said that he wanted to keep his mother's memory alive when he walked down the aisle.
Global fascination with the late princess -- who would have been 50 had she lived -- has fueled a public appetite for wedding coverage, particularly in the United States.
Watch a special two-hour "20/20" tonight at 9 ET as Barbara Walters takes a look back at the wedding watched by the world.
Just this week, William and Middleton made the emotional journey to Diana's grave at her family's 14,000-acre Althorp Estate. Holding hands, they laid flowers on the small island that is her resting place.
Other ghosts of that 1997 funeral are present today, even as Britons and Americans weary of a world at war and recession celebrate the happy event.
For the first time in 14 years, Elton John will return to Westminster Abbey, where the iconic British singer sang a haunting version of "Candle in the Wind" in tribute to his friend Diana. It later sold 33 million copies.
"The last time we were in Westminster Abbey, my heart sank when I saw those two boys walking behind the coffin," Elton told ABC's Barbara Walters of William and brother Prince Harry.
"And the next time we are in the Abbey it's to see him walking up the aisle with a beautiful woman and the love of his life," said John, who has since been knighted by Queen Elizabeth for his music. "I think it's the most joyous result and I'm sure Diana would be very, very happy about it."
Others on the guest list who hark back to Diana's days are former Prime Minister John Major, who was appointed to care for both the princes at her death, and her brother, Earl Spencer, and other family members.
Tessa Green, former chair of the Royal Marsden foundation, which was one of Diana's favorite charities, will also be in attendance.
Some would like to think that Middleton can fill Diana's shoes, as a beautiful and socially committed celebrity wife to the future king, but despite some similarities, the two are strikingly different.
And many hope that Middleton does not share the same ill-fated marriage. Charles and Diana divorced in 1996, the year before she was killed.
"[Prince William] really chose the Un-Diana," said Tina Brown, editor of Newsweek and the Daily Beast, and author of a book on Diana, told ABC. "Everything about Kate is counter-programming to his mother. I don't mean that he didn't adore his mother -- he absolutely did -- but there was so much drama, so much craziness, so much tragedy, really, in his life as a child growing up that he really needed somebody to be the anchor, not the drama, in his life."
Diana was just a shy, somewhat awkward 19-year-old teacher when she married Prince Charles, the heir to the British throne, on July 29, 1981.
Coming from an aristocratic British family, she was deemed suitable to marry into royalty. But Diana later confessed she was miserable on the night before her wedding, feeling isolated and cut off.
Some reports said Diana got cold feet right before the wedding and her sisters talked her out of backing out.
She barely knew Charles, meeting with him only 13 times before their wedding day, when her protected world changed overnight.
Middleton, on the other hand, was born a commoner, the daughter of entrepreneurs growing up in the village of Bucklebury, outside London.