The Vancouver native won 6-4, 6-4 against American Mackenzie McDonald on Friday in the junior boys semi.
Peliwo advanced in 75 minutes with five aces and four double faults, breaking on three of six occasions.
"I returned well and served well in the tough situations," said Peliwo. "I controlled the baseline and had good defence. I was able to put pressure on him.
Paliwo said there was nothing strange about facing his roomie for a chance at the biggest honour of his young career.
"We weren't allowed to room with our coaches, so when Mackenzie asked if I wanted to, I said sure," said Peliwo. "We didn't talk about the match last night; it wasn't awkward for us.
"There was no tension, we didn't want to rub it in each other's faces."
The final will be a re-match for the pair, with Peliwo beating Saville in the Traralgon junior event 160 kilometres from Melbourne only a week ago.
In the junior girls semifinal, Eugenie Bouchard from Westmount, Que., lost 7-5, 6-1 to Russian Yulia Putintseva.
Peliwo will next take on Australian Luke Saville at the Australian Open's main court — Rod Laver Arena. Saville advanced by winning 6-3, 6-4 over Czech Adam Pavlasek, who is supported by Andy Murray's Czech-American coach Ivan Lendl.
"It will be an experience to play on the Rod Laver arena, I'm looking forward to it," said Peliwo. "I've never been on a stage so big. The opponent will have the crowd with him, but I'm used to that by now."