The 23-month-old prince was pictured playing on the lawn, picking the grass and sliding down a hill with mum Kate at the Festival of Polo at the Beaufort Polo Club in Gloucestershire.
Autumn Phillips couldn't resist joining in the fun and played with George as he made his way down a slope.
Duchess Kate was pictured wearing casual jeans, a striped blue top and flat Sebago boat shoes at the event, while George was dressed in an all-blue ensemble of a cute cardigan, shorts and Crocs.
Kate looked relaxed as she ran after the toddler. The pair watched as Prince William took part in the polo.
There was no sign of six-week-old Charlotte and Kate and George walked over to Prince William who held his son as the couple chatted.
Zara Phillips, Mike Tindall and their daughter Mia Grace, along with Peter Phillips, his wife Autumn and their children Isla and Savannah joined Kate, William and George at the event.
At the Trooping the Colour on Saturday, George was pictured cheekily looking out of the window from the palace window as Kate attended the ceremony below.
All eyes were on the toddler as the royal family appeared on the balcony. Kensington Palace later confirmed that he wore the same outfit his father wore on the balcony at the Queen's birthday parade in 1984.