Exposure to extreme heat can lead to a range of heat-related illnesses, exacerbate pre-existing health conditions and cause increased demand on the healthcare system. A projected increase in temperature may lead to greater healthcare expenditure, however, at present the costs of heat-related healthcare utilization is under-researched. This study aims to review the literature on heat-related costs for the healthcare system with a focus on ED visits, hospitalization, and ambulance call-outs. PubMed, Scopus, and Embase were used to search relevant literature from database inception to December 2017 and limited to human studies and English language. After screening, a total of ten papers were identified for final inclusion. In general, the healthcare costs of heat extremes have been poorly investigated in developed countries and not reported in developing countries where the largest heat-vulnerable populations reside. Studies showed that exposure to extreme heat was causing a substantial economic burden on healthcare systems. Females, the elderly, low-income families, and ethnic minorities had the highest healthcare costs on a range of health services utilization. Although a few studies have estimated heat healthcare costs, none of them quantified the temperature-healthcare cost relationship. There is a need to systematically examine heat-attributable costs for the healthcare system in the context of climate change to better inform heat-related policy making, target interventions and resource allocation.