The goalkeeper has signed a five-year deal at Selhurst Park, joining the Eagles for a fee in the region of £20million having previously been linked with a return to Nottingham Forest.
Henderson joined United’s academy in 2011 and has been on their books ever since, though made only 13 first-team appearances and had loan spells with the likes of Stockport, Grimsby and Sheffield United, as well as Forest last season.
“Saying goodbye to United is an emotional moment for me,” Henderson posted on social media.
“This club has been a part of my life since I was a kid. From growing up as a United fan, to joining the academy aged 14, to stepping out on the pitch at Old Trafford!
“The journey has been a dream come true and I feel very blessed and fortunate to have fulfilled that dream.“
Henderson previously revealed he was “fuming” at United during the 2021/22 season, after spending the campaign as back-up to David de Gea and failing to get his chance to take the Spaniard’s place in the side.
He impressed while on loan with Forest last term, though he has not played since January due to a thigh injury.
“To the fans – your support has meant the world to my family and I,” Henderson continued.
“I’ve been United since I was a kid, and being able to wear the United badge on my chest has been an honour beyond words. I never took for granted the responsibility that came with wearing the shirt.
“We’ve had some highs and lows but I want to thank all of you for sticking by me throughout. Thank you for the memories and I wish the club all the very best for the future.”