The 29-year-old royal made the comment while chatting to radio presenter Virginia Araya at a party celebrating the Queen's official birthday in the Chilean capital of Santiago.
"I asked him what George was like," Virginia told Us Weekly. "He said, 'He's growing up. He is walking, and he has big, chubby cheeks. He looks like a young Winston Churchill.'"
CLICK ON PHOTO FOR HIGHLIGHTS OF PRINCE HARRY'S TOUR
At the party Harry was charged with giving a speech about his experience of the country.
Prince Harry remembers loss of his mother as he visits Brazilian orphans
Addressing the subject of Chile's tense World Cup match against Brazil, the fourth-in-line to the throne said he would be facing a "diplomatic challenge" over which side to support.
The Prince added that the topic of football back in the UK was "a very sore subject" given England's swift exit from the competition, although later that evening he saw Chile's World Cup hopes dashed as well when they lost out to Brazil on penalties.
Harry's week-long tour of Brazil and Chile drew to an end on Sunday 29 June.
Prince Harry watches England bow out of 2014 World Cup in Brazilian game
The Prince divided his time between the two South American countries, visiting hospitals, charities and environmental projects.
For his final engagement Harry visited a charitable foundation in Santiago that provides day care for children with mental and physical disabilities.