Off-spinner Patel and all-rounder Jimmy Neesham were the two players recalled to the squad on Friday, coming in at the expense of quick Matt Henry and batsman Dean Brownlie.
Selectors also confirmed that short-ball specialist Neil Wagner was fit for the series after a hand injury last month put him under an injury cloud.
As expected, there was no room for opening bat Martin Guptill, despite his unbeaten 180 this week in the fourth one-day international against the Proteas in Hamilton.
After returning home, he was discarded again for Test series against Pakistan and Bangladesh but has enjoyed a strong domestic season with Wellington.
Chief selector Gavin Larsen said Patel had the ability to turn the ball away from South Africa's left-handers, complementing fellow spinner Mitchell Santner.
"He brings a huge amount of experience to the team and gives us the balance of having two front-line spin options," Larsen said.
The first Test begins in Dunedin on Wednesday followed by two more in Wellington and Hamilton later this month.
New Zealand: Kane Williamson (capt) Trent Boult, Colin de Grandhomme, Tom Latham, Jimmy Neesham, Henry Nicholls, Jeetan Patel, Jeet Raval, Mitchell Santner, Tim Southee, Ross Taylor, Neil Wagner, BJ Watling.
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