The towering 32-year-old will join fellow pacemen Vernon Philander and Kagiso Rabada as well as left-arm spinner Keshav Maharaj in the Proteas' attack for the match at University Oval starting today.
Captain Faf Du Plessis admitted the selectors were taking a gamble by picking Morkel, who was ruled out of this year's Sri Lanka test series with a back injury.
"He looks good. If he is not going to be able play now, then we will never know if we don't take the chance. He is a fantastic bowler," Du Plessis said.
"All the reports say he is one hundred percent fine. He's bowled a lot of overs and he is pretty confident. He will just have to step out and see what he can do."
Morkel, who edged out Duanne Olivier as the third seamer, was picked in part to target New Zealand's three left-handed top order batsmen.
"That's one of the reasons he got the nod ahead of Duanne," Du Plessis said.
"You've got to make sure you pick your strongest team for the guys you are playing against.
"Bounce is a huge factor and the angle of the ball as it comes out of his hand - it goes either into right-handers and away from left-handers.
"He's terrible to face in the nets as a right-hander because you always feel like it's going to hit you in the ribs."
New Zealand captain Kane Williamson has held back naming an 11, saying he wanted to see the pitch on the morning of the match.
Selectors are likely to keep three seamers, but may opt to replace incumbent all-rounder Colin de Grandhomme with James Neesham, who has the edge in pace.
"They both provide different strengths. Colin can exploit that seam movement very well in surfaces and Jimmy can bowl with good pace and make things happen," said Williamson.