Housing retrofits are undertaken to reduce energy use and to improve ‘occupants’ indoor environmental conditions. Despite increased retrofitting of the Italian housing stock, there is a lack of data on their energy use and indoor environmental quality (IEQ). This paper fills this gap by a post-occupancy evaluation (POE) study of seven retrofitted apartments in northern Italy; a non-retrofitted case study was included as a comparison. The study aimed to understand aspects of IEQ and occupant satisfaction after energy-efficiency retrofits. A mixed-method approach encompassed occupant satisfaction surveys, energy bill comparisons, in-situ indoor air temperature, and relative humidity measurements. Results highlighted ‘occupants’ thermal comfort improvement and heating energy consumption reduction after retrofits. Furthermore, reported preferred indoor temperatures w within a broader range than the recommended Italian regulations and CIBSE guide A standard. However, some participants reported unintended consequences, including mould growth and noise from the mechanical ventilation system. This study shows the potential of POE to understand the actual performance of retrofitted residential buildings. However, the difficulties of conducting a POE in retrofitted existing residential buildings show the need of further research on how to effectively conduct POE in retrofitted residential buildings, including improved digital quality monitoring methods.