QPR have announced the signing of McCarthy from Reading on a four-year deal for an undisclosed fee.
Rs boss Harry Redknapp has tipped McCarthy, who won three caps for England Under-21s, as a future full international, and was thrilled to have captured his services.
"I am delighted to bring Alex in," he said.
"He's a great young goalkeeper with a great future in front of him. I think he's got the potential to be a future England goalkeeper one day, so to have him here at QPR is fantastic.
"I want to have competition for places in all areas of the pitch, and you can't have too much quality in your squad.
"He is a great signing for the club, and for the future of QPR."
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