Hosts Phillip Schofield, Holly Willoughby, Eamonn Holmes and Ruth Langsford were joined by the original presenters Richard Madeley and Judy Finnegan for the big live event, which was filmed from the show’s first home on Liverpool’s Albert Dock.
Sadly missing from the reunion was Fern Britton, who hosted the show from 1999 until 2009.
The beloved star had to miss out on the celebrations because of prior work commitments, but she sent a video clip wishing the show a very happy birthday, and sent her best wishes via Twitter, writing, "Here's to the next 25 years of brilliant broadcasting".
The two-hour programme saw a host of celebrity guests arrive to celebrate with the This Morning team, including Charlotte Church and Lee Ryan, who both launched their careers on the show.
Comedian Keith Lemon stepped on board the famous floating weather map, to the delight of the crowds gathered on the dock. And The Overtones were given the honour of closing the anniversary spectacular, singing their version of the Beatles classic, All You Need Is Love, in tribute to the city of Liverpool.
The event clearly meant a great deal to Richard Madeley, who, with his wife Judy, fronted the show from 1988 until 2001.
The evening beforehand he took to Twitter to share his excitement. "And so to bed… See you on This Morning, live from the Albert Dock 10.30 tomorrow," he wrote. "Haven’t said THAT since 1996 when show moved 2 London)."
Current hosts Philip and Holly said they felt honoured to be at the helm during the celebrations.
"Richard and Judy started the show and now for us to be in charge of it and seeing it through the 25th anniversary – which I never would have believed would have happened when it first began – is a real treat. I am very proud."
His co-presenter Holly added, "25 years is such an incredible achievement. I never ever thought I would be on the show now when I used to watch it when I was younger.
"But I am so proud to be working on This Morning. We cover so many varied subjects and if I wasn’t doing the show, I would be watching it. I feel guilty calling it a job because it is so enjoyable."