This study aims to assess the indoor thermal and environmental quality of low-income households in New South Wales, Australia. It adds evidence-based findings on the performance of residential buildings and contributes to improving the indoor environmental quality of social housing. The research presented in this paper involved subjective and objective evaluation of indoor air and environmental quality. The objective method included long-term monitoring of air temperature, relative humidity, and carbon dioxide during winter and summer 2018/2019, whereas the subjective method involved assessing occupants’ feedback about the indoor environmental quality. Physical observation of the indoor and outdoor conditions of each home was carried out on the same day of the questionnaire survey. Over 100 social housing households in the Greater Sydney area participated in this study. The characteristics of the specific population group are presented in this paper including details of energy bills, health, and indoor comfort. It further discusses issues related to the impact of urban overheating on indoor environmental conditions. Lower satisfaction rate with the thermal environment and poor indoor environmental quality affect health and quality of life of residents living in social housing. The minimum indoor air temperature recorded was about 5 °C during winter 2018 and the maximum indoor air temperature reached 39.8 °C in summer 2019. The mean thermal sensation vote increases by 1 point per 4.8 °C increase in the room indoor air temperature. The residents who participated in this study have an upper acceptable indoor air temperature of about 26 °C for 80 % satisfaction. This study highlights the need to improve both building quality and outdoor local climate. Acting on only one of the two sides is not enough to achieve nearly zero energy buildings in Australian climates, considering the predicted extreme weather conditions in future. Therefore, advanced mitigation and adaptation technologies are needed to improve the quality of low-income households, promotes health, and reduce energy for heating and cooling.