That historic win was expected to be Hook's last appearance of the summer as the 24-year-old prepared for shoulder surgery.
The Welsh Rugby Union had previously announced that Hook would miss next Saturday's Test against South Africa, as well as the impending tour of New Zealand.
But Wales coach Warren Gatland has performed a dramatic u-turn by naming the British & Irish Lions tourist in his starting XV for the Cardiff clash with the Springboks.
"James is desperate to play and it just shows how much it means to him to put that red jersey on," said Gatland.
"We are obviously delighted to have him and would particularly like to thank Scott Johnson and Andrew Hore at the Ospreys who have helped to make it possible.
"You only have to look at the man-of-the-match and player of the year awards James has been picking up to see what a great asset he is to any team and we will be facing the World Champions a stronger team because of his involvement."
Hook will start at outside centre for Wales, one position further out than where he impressed in the Grand Final win for his region.
But while he will face the World Champions, he won't be heading off on tour as his shoulder surgery will still go ahead this month.
There was bad news for one of Hook's Ospreys colleagues, however, with Shane Williams withdrawing from both Saturday's Test and the tour due to shoulder problems.
Williams' place on the plane to New Zealand will be taken by Dragons wing Will Harries, while Ospreys youngster Tom Prydie starts against the Boks.
Wales squad vs South Africa, Saturday June 5
Lee Byrne; Leigh Halfpenny, James Hook, Jamie Roberts, Tom Prydie, Stephen Jones, Mike Phillips; Paul James, Matthew Rees, Adam Jones, Bradley Davies, Deiniol Jones, Jonathan Thomas, Sam Warburton, Ryan Jones (captain)
Replacements: Huw Bennett, John Yapp, Alun Wyn Jones, Andy Powell, Richie Rees, Dan Biggar, Andrew Bishop
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