The iconic model, 48, got patriotic for the occasion, donning a Union Jack jacket alongside a chic black dress and red shoes.
Kate was part of the procession, dancing and blowing kisses to crowds of fans from an open-top bus alongside makeup legend Charlotte Tilbury.
A sweet video of the star also showed her posing alongside a bus emblazoned with her image as she prepared for the big pageant, which is one of the final parts of the weekend’s celebrations to mark Queen Elizabeth II’s 70 years on the throne.
The huge parade, which processes along the Mall and finishes at Buckingham Palace, features servicepeople, carnival dances, creative displays from arts organisations, and icons from the world of music, TV, film, comedy, and the arts.
Ed Sheeran will also perform the national anthem.
Kate recently testified in support of her ex, Johnny, at his defamation trial against his ex, Amber, which he won.
The model, who dated Johnny in the 1990s, testified via video link where she said rumours that Johnny had pushed her down the stairs in 1999 were untrue.
The former couple met in 1994 while in New York and embarked on a lengthy relationship before going their separate ways in 1998.
Kate was living it up (Picture: WireImage)
She waved to crowds of fans (Picture: AP)
Kate was seen alongside Patsy Kensit (Picture: REUTERS)
The procession marks one of the final events of the Jubilee celebrations (Picture: Chris Jackson – WPA Pool/Getty Images)
Kate had been brought up by Amber on the stand, with the actress claiming she’d heard rumours about Johnny pushing her down the stairs during their relationship, which flashed through her mind as he allegedly argued with her sister Whitney near some stairs, leading Amber to lash out and hit him.
Kate told the court that there had been a ‘rainstorm’ and as she left her hotel room, ‘I slid down the stairs and I hurt my back.’
The supermodel went on to testify: ‘He never pushed me, kicked me or pushed me down any stairs.’
Kate Moss testified during the trial (Picture: REUTERS)
Johnny Depp won the trial (Picture: Getty Images)
Amber Heard said she was ‘heartbroken’ after the verdict (Picture: AFP via Getty Images)
Kate Moss and Johnny Depp dated in the 1990s (Picture: WireImage)
The fashion icon has never alleged that she was abused by her ex during their lengthy romance, but has said that she cried for ‘years’ after their split.
The actor was ultimately awarded $10million (£8million) in compensatory damages, and a further $5million (£4million) in punitive damages, while Amber won one of her three defamation countersuit claims, and was awarded $2million (£1.6million).
The Depp and Heard trial began when the actor sued his ex-wife for $50m (£39.93m) after she wrote an op-ed for The Washington Post speaking about her experiences of domestic violence.
While he was not named in the article, his team argued that it was implied that he was sexually and physically abusive towards her in their relationship, which he denied.
The Aquaman actress later countersued her ex-husband, claiming that he libeled her by calling her a liar, seeking $100m (£79.86m) in damages.
The former couple were married from 2015 to 2017.
More: Johnny Depp
Johnny had flown to the UK before the verdict came in and has been performing with friend Jeff Beck on his tour.
Kate is thought to have attended the pair’s show at the Royal Albert Hall in London.
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Queen Elizabeth II’s Platinum Jubilee 2022
Dust off your Union Jack bunting, Queen Elizabeth II’s Platinum Jubilee is well and truly upon us.
Taking place from Thursday, June 2, to Sunday, June 5, the celebrations mark Her Majesty’s record-breaking 70th year on the throne.
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Visit Metro.co.uk’s Platinum Jubilee page for all the latest updates.