He currently plays for HK Kópavogur, wearing the number 5 shirt. At the international level, he represents Iceland U20. He plays primarily as a Defender. His current market value is estimated at 50K €.

His most recent move was a from Valur Reykjavik to HK Kópavogur on 2025-02-15.

Throughout the Iceland 1. Deild Karla 2025, thorsteinn antonsson featured in 21 matches, averaging 0 tackles, 0 interceptions, and 0 clearances per game, while blocking 0 shots per game.