In the cute picture, the nine-year-old could be seen sitting next to a huge soft toy rabbit who was bigger than she was.
The bunny wore a dark T-shirt with a pink logo advertising Inter Miami, the football team David shares ownership of, as well as a matching cap.
David captioned the image: "Someone’s a @intermiamicf fan #HarperSeven and Celine [laughing emoji]... Harper seven - we love your team daddy."
The official Inter Miami account responded with a heart-eyes emoji, and many of the dad-of-four's fans posted heart emojis in response.
WATCH: Harper Beckham films herself giving a fabulous behind the scenes tour
Other followers commented: "Harper [red heart emoji]," "Harper love you so much," and: "Me too, love you and your team. Best Dad."
As well as young Harper, David shares three sons with his wife Victoria: Brooklyn, 21, Romeo, 18, and Cruz, who is 15.
The doting parents met when David was a Manchester United footballer player and his wife was a member of the Spice Girls and tied the knot in 1999.
David shared the sweet photo of Harper to Instagram
David is a devoted dad and is clearly keen for his daughter to enjoy football as much as he does, as the pair were spotted together in the stands during the Women's World Cup.
Earlier this summer, the 45-year old shared a short video showing Harper practising her football skills at the family's Cotswolds home, where they spent lockdown.
David and Victoria enjoyed a change of scene this week, thanks to their lavish German wellness retreat.
The couple headed to Villa Stéphanie in Baden Baden in Germany's Black Forest for their special detoxing break.
They shared some behind-the-scenes glimpses of the trip to Instagram Stories, with Victoria looking radiant in one snap as she posed with "minimal makeup" before "a day of hiking".
Another photo saw the couple perched on a rock, with David sweetly wrapping his arms around his wife. Aww!
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