He is on the books of HK Kópavogur and wears shirt number 5. At international level, he features for Iceland U20. His main role on the pitch is Defender. His estimated market valuation currently stands at 50K €.

His latest transfer saw him join HK Kópavogur from Valur Reykjavik via on 2025-02-15.

Across the Iceland 1. Deild Karla 2025, thorsteinn antonsson appeared in 21 matches and averaged 0 tackles, 0 interceptions, 0 clearances, and 0 blocked shots per game.