Kisnorbo's contract was due to expire at the end of the 2014-2015 campaign, having signed a one-year extension last April.
But van 't Schip said on Friday the lion-hearted defender would saddle up for a third season with City.
"Patrick is still contracted for one more year and is going to be with us next year," he said.
After featuring in all f City's A-League matches this season, Kisnorbo has crossed a threshold in his existing contract to earn a new deal.
On Wednesday, the defender brushed off talk of staying on, saying he "wasn't really worried about next year.
I'd love to stay at the club. It's a great club with a big future."
Van 't Schip confirmed why Kisnorbo, with just a few weeks remaining on his current deal, was so relaxed.
The 34-year-old could have a new central defensive partner on Sunday for the visit of Wellington.
Connor Chapman is available for selection after serving his suspension for manhandling a referee in City's last loss, a month ago to Western Sydney Wanderers.
That doesn't mean the 20 year-old will resume duties in the heart of City's defence, according to Van 't Schip.
"We have to see if we're shuffling him back in. Why shuffle him back in if, in the last four games, we've had good results?" he said.
"We have to analyse good what the team looks like, what the players look like and we'll make a decision on Sunday."
With City having picked up 10 points from the past four matches, Kew Jaliens could be favoured to continue a role alongside Kisnorbo.
Van 't Schip has warned his side to expect a fiercely competitive match against the Phoenix, City's last home game of the season.
"Wellington want to prove something after their two losses at home," he said.
