The Vancouver native defeated Czech Adam Pavlasek 2-6, 7-6 (5), 6-0 in the boys semifinals at the French Open on Friday.
Peliwo is determined not to let his nerves get the best of him as they did five months ago when he lost the Australian Open junior final to local Luke Saville.
The fifth-seeded Peliwo will face No. 6 seed Kimmer Coppejans of Belgium, who defeated eighth-seeded American Mitchell Krueger in the other semi.
"I hope to jump in, get a good start and follow through," said the 18-year-old Peliwo. "I've got to get this one. I'd feel pretty bad if I lost two in a row. But I think I can win it."
Peliwo, who lost in the second round at Roland Garros a year ago, spent just under two hours fighting off Pavlasek, who is the boyfriend of Wimbledon champion Petra Kvitova.
As Kvitova left the sparsely populated stands for a snack, her man's game seemed to fall apart, with Peliwo dominating the third set to win it on his third match point after the Czech's backhand went long.
When he was almost down and out, Peliwo said he realized he had nothing to lose.
"In back of my mind I knew I was in a bad situation and it was probably over, I just went for my shots and connected on a couple of returns," he said. "I just stepped in and hit it hard. That first break in the third set got me going. I tried to keep the same attitude and energy and put pressure on him, he broke down and probably got nervous."
Peliwo said that he plans to relax and try not to think about Sunday too much.
"I'm not going to think about it all the time, I'll try to get it off my mind," he said. "When I have to start preparing for the match, I will. I don't want to make the mistake I did in Australia when I thought of it 24/7.
"There I was like 'Oh my God I'm in the final.'"