The middle of the first millennium AD in Sweden witnessed significant changes in the archaeological record, prompting various discussions about the underlying causes. This paper reviews the research developments surrounding the global climate cooling, which was caused by severe volcanic eruptions in AD 536/540 and is referred to as the Late Antique Little Ice Age or Fimbulwinter, and its potential impacts, with a specific focus on Swedish Iron Age societies, drawing upon published climatic and archaeological data. Furthermore, it discusses the research gaps that impede a comprehensive understanding of the potential relationship between the AD 536/540 event and socioeconomic changes in Iron Age Sweden. Additionally, it suggests that isotopic analysis will offer additional insights and help bridge the research gap.