With several adult teeth grown in and his sandy blonde hair parted down the side, George looks more like his father than ever in the new portrait.
"The future king is so handsome! Just like his dad, the Duke of Cambridge," one penned on the Instagram post.
But his smiling brown eyes were a genetic gift from the Middleton family, with royal watchers often commenting how much he resembles uncle James Middleton.
Another wrote on Twitter; "Just like his dad, but there's plenty of Catherine in him too. Just look at that sweet smile!"
George turns nine on July 22, marking another milestone birthday for the young royal.
Since turning eight last year, he's attended a number of key public events with his parents and taken his first steps into public royal life.
While Catherine and William are clearly eager to protect their eldest son from the pressures of life in the spotlight, they have taken to bringing him along to "fun" royal outings.
He has attended a number of sporting matches with his parents, delighting fans when he arrives without warning in darling little suits and cheers from the stands.
WATCH: Kate Middleton's sweet moment with Prince George at Wimbledon
George also stepped out for Wimbledon this year, where he charmed officials with polite handshakes as mum Catherine showed him around the venue.
It's believed the outing was a special treat for George's birthday; Catherine told reporters his younger sister Princess Charlotte stayed home as "It's George's treat today".
George had been hoping for Djokovic to win according to dad William, who stepped in when George shied away as reporters asked who he was backing.
"Djokovic," he whispered to his son, before cheekily adding: "We'll see how long it lasts. He'll support the winner."
This article first appeared on our sister site, Now To Love.