Magnús played 57 games for the Icelandic national team from 1987 to 1994. In his last game, he scored 11 points in a 105-100 victory against England, where the English players stormed off the court with 24 seconds left due to their unhappiness with the referees. In March 1995 he was selected to the 19-player training camp but was not among the players selected for the team.