The young right-back is completing a big money move from Crystal Palace to the Red Devils this week.
Rooney, who spent more than a decade at United, had some wise words for the 21-year-old ahead of the move of his life.
Rooney told Wan-Bissaka on Sky Sports: "Enjoy it. Play with no fear.
"Manchester United's a fantastic club. One of, if not the best football club in the world.
"You have to embrace it, embrace the culture of United.
"Learn the history and do your best. I'm sure he'll be fine. The coaches there will be telling him all of this."
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