He is on the books of Grotta Seltjarnarnes and wears shirt number 27. His main role on the pitch is Midfield. His stronger foot is Right.

His latest transfer saw him join Grotta Seltjarnarnes from Valur Reykjavík Youth via on 2026-04-06.

Over 2 appearances in the UEFA European U17 Football Championship 2025-2026, Mattías Kjeld contributed 0 goals and 2 assists, completed 0 key passes from 0 total passes, and posted a passing accuracy of -.