Asked whether he and his wife, Kate, are planning to expand their family, William said: "Maybe one day. One's enough at the moment."
A soldier asked the prince the question Monday as the royal couple visited the Irish Guards at their military base in Aldershot in southern England to mark St. Patrick's Day.
Kate, dressed in an emerald green trench coat with matching hat and heels, presented sprigs of shamrocks to around 300 soldiers on parade. She also placed a bunch on the regimental mascot, Irish wolfhound Domhnall.
William and Kate's baby son, George, will be joining them on their trip to New Zealand and Australia next month.