The 1998/99 season of the Extraliga was the sixth regular staging of the top division of ice hockey in Slovakia . In the playoff final, HC Košice prevailed against HC Slovan Bratislava with 3-1 victories and thus won the third Slovak championship title in the club's history. The league was reduced from twelve teams to eight for the following season. Therefore, after a first group phase, the league management let the two best-placed teams in the second-rate 1st division , HK Spartak Dubnica and MsHK Žilina with the lower half of the Extraliga play out the two teams that were allowed to participate in the Extraliga next year, as well as at the playoffs of the 1998/99 season. The six best teams in the Extraliga in the first group phase played out the playoff placements among themselves.
Champion of the 1998/99 season was HC Košice, who won the best-of-five series against HC Slovan Bratislava with 3-1 wins and won the third Slovak championship title in the club's history.