Mateiko signed a three-year, entry-level contract with the Capitals on Friday, per PuckPedia.
Mateiko had 23 goals and 43 points in 49 contests with QMJHL Saint John in 2023-24. He was taken by Washington with the No. 90 overall pick in the 2024 NHL Draft. Mateiko is projected to spend the upcoming campaign in the QMJHL.