Walsall have pounced to sign the striker, who lifted the Vanarama National League Golden Boot as we as the play-off trophy at Wembley.
Dean Keates, the former Wrexham manager, of course knows all about Cook and was quick off the mark.
"He’s somebody I’ve admired for a long time," he said.
"As soon as I got the job here and knew he was out of contract I made him my primary target. I’m delighted to have gotten this over the line as there were plenty of clubs in for him – his record speaks for itself – and I’m looking forward to working with him.
"I have no qualms about him stepping up to League One."
Cook told the Saddlers official website that he can’t wait to get going.
"I’ve scored 51 goals in the last two years at National League level and now I want to prove myself in the EFL,” he said.
"This is a big step up to a big club. I know the manager from his time at Wrexham and I know what he is about; I’m excited by the challenge and where he wants to take the club."
Tranmere manager Micky Mellon said: “We would have loved to have had Andy with us back in the Football League but he wanted to test himself at a higher level.
“We hope he is as successful at his new club as he was with us.”