Halldórsson was unable to translate his indoor win to an outdoor one at the 1978 European Athletics Championships, placing eighth. His season's best of again ranked him in the top five globally. There were no major events for him to aim for in the 1979 season, but his throw of that year ranked him in the global top ten. His highest placing at a world-level event came at the 1980 Moscow Olympics, where he threw in qualifying, then in the final for tenth place. The latter performance was a metre down on his best that season. In his final top level international competition he was sixth at the 1981 European Athletics Indoor Championships.