Fellow Greenmeadows pupil Tori Gibbs was a runner-up in the competition.
Leatherman was greeted by school principal Mark Johnson, while students and staff performed a full waiata and haka at his arrival.
"I've never experienced anything like this before, so it was amazing to see such a wonderful performance," Leatherman said.
He presented Charlotte with her prizes as well as a $1000 cheque for the school and described her reaction as "wordless".
"I asked her what she was going to spend her $200 on and she was very quiet. I think she was just very shy," he laughed.
Leatherman said he picked her design because it was "semi-practical".
"The way she laid out the ideas in the tools, the way she had everything folding in and out showed some real engineering as well as real creativity."
The multi-tool was created by Leatherman in 1975, when he found himself constantly needing to fix things, but never had the right tools.
Thinking it would take him a months to design, it took him three years.
Thirty-five years after the tool's creation, he's sold 75 million around the world.
New Zealand is the eighth country he's visited for his anniversary celebration. He will be visiting schools in Auckland today before flying down to Christchurch.