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.
"They're just a natural, normal family like the rest of the people that come in here, down to earth, lovely family, very polite, very nice," John Haley, the landlord at the local pub, the Old Boot told ABC.
At 29, she is university-educated, the first to marry a future king and to hold a degree. She met Prince William, who is 28, during their days at St. Andrews University in Scotland.
They have known each other well, first as friends, then living together. Their courtship has lasted nine years, which is why the tabloid press gave the bride the nickname, "Waitie Katie."
Still, Diana had an independent streak that echoes through many of Middleton's lifestyle choices.
Middleton, like her late mother-in-law, has made it clear she's "of the people," sighted in recent days on the High Street buying a dress from Banana Republic.
And William may have seen in Middleton the sense of flair that his mother exhibited -- not only in fashion, but in her joie de vivre.
Both wore feathers in their caps and were often seen in red and black with hats to match. They loved red polka dots and nights on the town. Diana took her boys skiing in the Alps, not unlike the new royal couple.
But while Diana and Charles accepted 6,000 gifts on their wedding day 30 years ago, the new royal couple has asked for donations to charity.
Just like his mother, William has remembered the Child Bereavement Charity, asking that invitees donate instead of sending gifts.
The gesture is bittersweet: The charity reaches out to children who have a lost a parent.
Said Prince William in 2009, when he became a royal patron to the charity, "What my mother recognized then -- and what I understand now -- is that losing a close family member is one of the hardest experiences that anyone can ever endure...Never being able to say the word 'mummy' again in your life."