Talking to Britain's Sky News for the new documentary The Queen At 90, he praised his granny for helping him and brother Prince Harry after the death of their mother Princess Diana in 1997.
"She's been a very strong female influence," he said of the monarch, who marks her 90th birthday on Thursday, "and having lost my mother at a young age, it's been particularly important to me that I've had somebody like the Queen to look up to and who's been there and who has understood some of the more, um, complex issues when you lose a loved one.
"So she's been incredibly supportive and I've really appreciated her guidance."
Diana died in a car crash in Paris in 1997 – when William was just 15 and Harry was 12. Next year will be the 20th anniversary of the tragedy.
On a much different note, William also shared another impactful memory involving his grandmother, whom Harry recently called "the boss".
Max Mumby / Indigo / Getty
During a visit to Balmoral Castle in Scotland, he and cousin Peter Phillips were riding a quad bike around the estate alongside Peter's sister Zara.
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"We were chasing Zara around who was on a go-cart, and Peter and I managed to herd Zara into a lamppost," William recalled. "And the lamppost came down and nearly squashed her, and I remember my grandmother being the first person out at Balmoral running across the lawn in her kilt.
"[She] came charging over and gave us the most almighty bollocking, and that sort of stuck in my mind from that moment on."
The Queen at 90 airs in the U.K. at 9 p.m. Wednesday.