Jón competed in track and field[5] from the age of 18 until the age of 39, winning several Icelandic championships in long jump, triple jump, high jump, pentathlon and relay racing.[4] He was first noticed on the national stage when he competed in the Meistaramót Íslands in 1978 where he medaled in long jump and triple Jump.[6]
Football
Jón played for several seasons in the Icelandic top-tier football league, then named 1. deild karla. In 1979, while playing for KR, he was the fifth highest goal scorer ins the 1. deild with 8 goals.[4]
Jón played three seasons in the Icelandic top-tier Úrvalsdeild karla, winning the Icelandic championship and Icelandic Basketball Cup in 1980 as a member of Valur.[4] He played for several seasons in the lower leagues. On March 6, 2009, he played his last game at the age of 50, in the second-tier 1. deild karla.[9]