Southee limped out of the tour match against England Lions at Grace Road with a sore left toe and has since seen a specialist and undergone scans in London.
Without him, the Kiwis would have had to rely on their two left-arm seamers, Trent Boult and Neil Wagner, and the fit-again Doug Bracewell. Twenty-four-year-old Southee is their most tried-and-tested, however, with 24 Tests under his belt, and coach Mike Hesson confirmed that he will be available after all on Thursday.
"Tim's fine. It was very much a precautionary response really from us," he said.
"We sent him down to London for further investigation, and basically the result was as we hoped.
"He's had some treatment to his left toe, and we're very comfortable he'll be right for the first Test."
Wagner might have played in any case, as New Zealand's leading wicket-taker in the three recent draws.
He too has recovered from a minor toe injury and Hesson said: "It will be very hard to leave him out. Neil is very much in consideration to play."
Wagner could do so as part of a four-man seam attack, should New Zealand decide conditions mean they can sacrifice left-arm spinner Bruce Martin.
"Absolutely. That's an option," added Hesson. "Whoever is left out, it will be a tough decision."