The images show the prince in the grounds of Anmer Hall, aon the Sandringham Estate.
They were taken in mid-July by photographer Matt Porteous. One shows the prince offering an ice cream to the family dog, Lupo. Another shows him playing on a swing.
Mr Porteous, who is from Jersey, describes himself as a commercial lifestyle, wedding and underwater photographer in an online profile.
A Kensington Palace spokesman said: “The Duke and Duchess hope that people will enjoy seeing these new photographs.
“They would like to thank everyone for all the lovely messages they have received as Prince George celebrates his third birthday.”