Alongside Kate and husband Prince William, other royal guests included Prince Harry and Princess Eugenie.
However, the Middleton family reportedly did not want Meghan Markle to attend.
In December 2018, The Sun's royal correspondent Emily Andrews wrote: "Meghan faced some opposition from the Middleton family, who did not want to invite her to Pippa's wedding last May.
"They feared Meghans first public appearance with Prince Harry would overshadow the bride's big day."
In the event, Meghan only appeared for the evening reception, after Harry made a 50-mile dash to collect from Kensington Palace in time for the celebrations.
The lavish party included a Spitfire fly-past the Middleton's home village of Bucklebury, which cost an estimated £ 700,000.
A source at the time said: “[Harry] left as discreetly as possible and traveling with her back, showing just how serious he is about her.
"He didn't want Meghan to arrive along, without him alongside his, at the reception."
The news first broke of Harry and Meghans romance in October 2016, when a source told the Sunday Express that Harry was "happier than he was for many years" and "besotted" with Meghan.
Royal expert Angela Mollard, speaking on podcast "Royals" in 2018, commented: "A private secretary phoned and said:" Look, the word's out. This has leaked. "
"He apparently turned to Meghan and said:" Things will never be the same again. "
"He knew that. He knows what he's like, he’s seen it with his brother, he’s seen it with his previous girlfriends.
"I can imagine he felt a little bit of sadness that had privacy [gone]."
The future Duke and Duchess of Sussex made their first ever public appearance together at a polo match at Ascot in May 2017.
However, the Invictus Games opening ceremony in Toronto.
It later emerged that Harry and William had momentary friction in their relationship, when the Duke of Cambridge asked his brother about the peace at which his romance was developing.
A source told Ms Andrews: "He just wanted to stress that he was part of the Royal Family." Was Meghan the right one? "
Another courtier added: "A lot of people in the family objected.
"Harry stood up for Meghan very forcibly. He really loves her. "
Harry and Meghan's joy was infectious at their unforgettable royal wedding in Windsor last year, which was watched by nearly 2 billion people worldwide.
Ahead of the birth of Archie Harrison last month, the couple moved from Kensington Palace to their new family home at Frogmore in Windsor.
However, the Duke and Duchess of Sussex have recently undergone scrutiny for the amount spent on their new home, with £ 2.4million spent on renovation works.
Baby Archie's christening is set to take place early next month.