Schwärzler won the Austrian U18 national championship titles in singles and doubles in 2022, and followed this up by winning the U16 European Championships in July 2022 in
Přerov, Czechia, defeating top seed
Martín Landaluce in the final. In September 2023, Schwärzler was a runner-up in the
boys' doubles category at the
2023 US Open, with Italian
Federico Bondioli. The pair lost to
Max Dahlin and
Oliver Ojakäär, despite twice having a match point. In October, Schwärzler won two singles titles in a row, claiming victory at J500 event in
Osaka and following that up with victory at the
ITF Junior Masters event in
Chengdu, China. He defeated Mexican
Rodrigo Pacheco Méndez in the boys’ final. He became the first Austrian player to win the title. At the
2024 French Open, Schwärzler won his first
Grand Slam Junior title, in the boys' doubles, partnering with Norwegian
Nicolai Budkov Kjær. The Austrian had good results on the
ITF junior circuit, maintaining a 105–46 singles win-loss record and reached an
ITF junior combined ranking of world No. 1 on 29 January 2024. ==Professional career==