Princess Charlotte has been giving the Duke of Cambridge "a few sleepless nights", he has admitted.
William made the remark to the England football women's team before they flew out to a tournament in Canada.
He was also presented with a miniature replica of the side's kit for the princess, bearing her name and the number "1" on the back.
Steph Houghton, who captains the side, said the Duke had been telling them about domestic life with new arrival Charlotte, and older sibling Prince George.
"He said George is very lively, and Princess Charlotte has been keeping him up all night, giving him a few sleepless nights," said the 27-year-old.
"But he said he was just happy to have them both here."
William, who is president of the Football Association, met the Lionesses' head coach, Mark Sampson, and the senior women's squad at St George's Park in Staffordshire.
In a lighter moment, Aston Villa fan William quipped to players he might be left having "a bad day" after the FA Cup final is played on May 30, with Villa playing Arsenal for the trophy.
As FA president he will be responsible for handing the cup to the winning side's captain, at Wembley.
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