Sharing a stunning photo of the 29-year-old Princess of York at the event, the account - which is followed by almost four million people - captioned the shot:
"Princess Eugene speaks to a group of young people about how they achieved their Gold Award.
"The @DofE has inspired millions of young people to serve their communities, experience adventure and develop and learn outside of the classroom."
The tweet, which should have read Princess Eugenie, was swiftly deleted and reposted with the correct spelling.
Princess Eugenie's appearance at her grandfather's event came after a mysterious stint away from the spotlight.
Her absence from major events including the wedding of Lady Gabriella Windsor and the Duchess of Cambridge's Chelsea Flower Show exhibit prompted renewed rumours she is expecting her first child.
Check out this video to see why everyone is CONVINCED Eugenie is pregnant!