He is on the books of Unia Skierniewice and wears shirt number 18. His main role on the pitch is Forward.

His latest transfer saw him join Unia Skierniewice from MKS Notec Czarnkow via Free on 2026-01-31. The move was reported at 0.005M €.

During the Poland Liga 2 2025-2026 campaign, Jan mierzwa made 1 appearances, scoring 0 goals and adding 0 assists. He averaged 0 goals per match from 0 shots, with 0 on target.