He is on the books of HK Kópavogur and wears shirt number 29. His main role on the pitch is Forward. His stronger foot is Left. His estimated market valuation currently stands at 50K €.

His latest transfer saw him join HK Kópavogur from HK Kopavogs U19 via on 2022-05-11.

During the UEFA European U19 Football Championship 2025-2026 campaign, Karl Ágúst Karlsson made 1 appearances, scoring 0 goals and adding 0 assists. He averaged 0 goals per match from 0 shots, with 0 on target.