The 16-year-old had been hopeful of competing in the women’s event, but lost out during the latter stages of qualification.
Robson put on a determined display against Pliskova, winning 6-3 6-1 in just over an hour to set up a clash with Pliskova’s twin sister, Karolina on Saturday morning.
The Brit will be looking to go one stage further after she lost out in the final of the same competition last year.
Speaking after her victory, Robson said she believes her game has improved over the last 12 months.
“I think I’ve really improved since last year in all aspects, especially my movement,” she said. “I also feel more comfortable on court.”
“I’d love to win a second junior Grand Slam.”
She also voiced her support for Andy Murray, who will play in the second Grand Slam final of his career on Sunday morning.
“He’ll be pretty confident going into the match as he’s played so well so far. It would be really good for British tennis (if he won),” she concluded.
The final of the junior championships is scheduled to get underway in the early hours of Saturday morning at 0200GMT.
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BIOGRAPHY: Daniel Sturridge
BIOGRAPHY: Kepa Arrizabalaga