The 22-year old Italian striker has signed a three-year deal with the Bluebirds whom he will join officially when his Old Trafford deal runs out at the end of June.
Macheda, who initially joined United's academy in 2007, was thrilled to be starting anew after experiencing a number of loan deals since 2011 which such clubs as Sampdoria, QPR, Stuttgart, Doncaster Rovers and Birmingham City.
"It's a massive opportunity for me and it is with thanks to Ole Gunnar Solskjaer that I am here," he told Cardiff's official website.
"Last season I had a good spell on loan at Birmingham City, but this is a new chapter of my career now and I can't wait to get started and show everyone who I am.
"Knowing (Cardiff manager) Ole (Gunnar Solskjaer), he wants to get back into the Premier League as soon as possible and the recent signings show that.
"I'm here for the same reason. I feel that this is a great team and if we can have a good season and work hard then we can go straight back up."
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