He is on the books of Inter Milan U19 and wears shirt number 15. His main role on the pitch is Defender. His stronger foot is Left.

His latest transfer saw him join Inter Milan Primavera from Grasshopper Club Zürich U19 via Transfer on 2025-08-27.

Across the UEFA Youth League 2025-2026, Joachim Williamson appeared in 5 matches and averaged 0.2 tackles, 0.2 interceptions, 0.2 clearances, and 0 blocked shots per game.