Josha Vagnoman was born in Hamburg, Germany, and began his football journey at the Hamburger SV academy, joining the youth setup in 2010. He made his professional debut for the first team on March 10, 2018, in a Bundesliga match against Bayern Munich, becoming the youngest player to ever play for Hamburg in the top flight at just 17 years and 89 days old. Over the following seasons, Vagnoman faced challenges with injuries but managed to secure a consistent role as a right-back, finishing his time at Hamburg with 24 league appearances in the 2020–21 season, during which he scored two goals.
In July 2022, he signed a four-year contract with VfB Stuttgart, marking a new chapter in his career. Vagnoman made an immediate impact, starting in his debut match for Stuttgart in the DFB-Pokal and continuing into the Bundesliga. Known for his solid defensive skills and ability to contribute to attacks, he plays a crucial role for Stuttgart as they aim for success in the Bundesliga.
On the international stage, Vagnoman has represented Germany at various youth levels and received his first senior call-up in March 2023, marking his debut at the senior level shortly thereafter.