Eugenie, 32, is pictured standing with husband Jack Brooksbank, 36, who is holding their one-year-old son August.
The smartly dressed trio are standing on a London rooftop waving to the aircraft, at what appeared to be a jubilee celebration party.
The images posted to Instagram, which include a video of the Red Arrows flying over as cheering can be heard in the background, is captioned: “The most perfect day to celebrate 70 years.”
Followers posted comments including “Absolutely beautiful” and “aww bless, look how big August has got, sharing in the celebrations of our gracious Queen on her platinum Jubilee celebrations”.
Others filled the comments section with love heart emojis.
The princess, the Queen’s granddaughter and the daughter of the Duke of York, is 12th in line to the throne.
Eugenie and Mr Brooksbank, a bar manager, married in 2018 in St George’s Chapel at Windsor Castle in 2018.
In February 2021 she gave birth to August at the Portland Hospital in London.
He was christened in November at the Royal Chapel of All Saints in Windsor Great Park at a private service attended by the Queen.