Kensington Palace tweeted a new photograph of William with his three children: Prince George, 6, Princess Charlotte, 5, and 2-year-old Prince Louis.
It said William's wife Kate, the Duchess of Cambridge, 38, took the picture earlier this month.
William is second in line to succeed his grandmother Queen Elizabeth II, 94. His father Prince Charles, 71, is first in line.
He is the eldest son of Charles and the late Diana, Princess of Wales, who died in a car crash in 1997.
William served in the British armed forces for seven and a half years in his 20s, training as a helicopter pilot.
In recent years, he has raised his profile as a supporter of mental health, homelessness, conservation and other charities.
It said William's wife Kate, the Duchess of Cambridge, 38, took the picture earlier this month.
William is second in line to succeed his grandmother Queen Elizabeth II, 94. His father Prince Charles, 71, is first in line.
He is the eldest son of Charles and the late Diana, Princess of Wales, who died in a car crash in 1997.
William served in the British armed forces for seven and a half years in his 20s, training as a helicopter pilot.
In recent years, he has raised his profile as a supporter of mental health, homelessness, conservation and other charities.