The photo's caption reads: 'Happy Father’s Day! And wishing a very special first Father’s Day to The Duke of Sussex!'
Unlike Australia which celebrates Father's Day in September, the UK Father's Day was yesterday (June 16 2019).
In the past it's been rumoured that the Instagram account is run by Meghan Markle the Duchess of Sussex herself, but she wasn't seen in the photo.
It was a big weekend for baby Archie as the plans for his christening were also officially announced.
The newest member of the royal family will be christened at St George’s Chapel at Windsor Castle, where Meghan and Harry married in May last year.
The christening will take place in July when Archie is two months old. The chapel is the same place where Prince Harry was christening in 1984 and tipped to be one of the biggest royal events of the year.