Ballhaus competed in the 48 kg category from 2016 to 2019. In 2016 she was third at the Cadet European Championships. In 2017 she won the individual and team competitions at the Cadet European Championships and finished second at the Cadet World Championships.[3] In 2018 and 2019 she finished fifth at the Junior European Championships.
In 2020, Ballhaus moved up to the 52 kg weight class. In November 2021 she finished second at the U23 European Championships behind Croatian Ana Viktorija Puljiz.[3] In April 2022, she reached the semifinals at the European Championships in Sofia. After the semifinal defeat against the British Chelsie Giles, she lost to against Distria Krasniqi from Kosovo for the bronze.[3] In January 2023, Ballhaus won her first German championship title. At the same championships, her twin sister Seija Ballhaus won in the weight class up to 57 kg division.[4]
In March 2023, Mascha Ballhaus won the final of the Judo Grand Slam Tashkent against the Japanese Ai Shishime.[5] At the European Championships in Montpellier, she lost in the quarterfinals to the French Amandine Buchard. With victories over the Israeli Gefen Primo in the repechage round and over the Italian Odette Giuffrida in the fight for third place, Ballhaus won a bronze medal.[3] At the 2024 World Championships in Abu Dhabi, she lost in the quarterfinals to Amandine Buchard. With victories over Brazilian Larissa Pimenta and Japanese Hibiki Shiraishi, Ballhaus secured a bronze medal at the World Championships.[6]
At the 2025 World Championships in Budapest, Ballhaus, won another bronze medal.[7]
(2024, 2025)
(2023)
