The 96-year-old monarch met her 11-month-old great-granddaughter – who is the youngest child of the Duke and Duchess of Sussex – at Windsor after the royals attended Trooping the Colour, the Daily Mail newspaper reports.
The duke and duchess – who also have a three-year-old son called Archie – have returned to the UK for the Queen's Platinum Jubilee celebrations.
The couple, who tied the knot in 2018, are now based in California, after they stepped down as senior members of the royal family in early 2020.
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They said in a statement at the time: "We intend to step back as 'senior' members of the Royal Family and work to become financially independent, while continuing to fully support Her Majesty The Queen."
The duke and duchess also attended the Jubilee service at St Paul's Cathedral today.
However, the monarch was absent from the service after she suffered “discomfort” while watching a parade at Buckingham Palace.
The Queen watched a military parade and waved at well-wishers gathered on The Mall, but she subsequently withdrew from the service at St Paul's.
In May, the Queen also missed the state opening of parliament.
The monarch has been experiencing mobility issues in recent months and Prince Charles assumed the responsibility.
A Buckingham Palace spokesperson said at the time: "The Queen continues to experience episodic mobility problems, and in consultation with her doctors has reluctantly decided that she will not attend the state opening of parliament."
Meanwhile, a Downing Street spokesperson said: "The prime minister fully respects the wishes of Her Majesty and is grateful to the Prince of Wales for agreeing to deliver the speech on her behalf."