The indoor climate in commercial kitchens is often unsatisfactory, and working conditions can have a significant effect on employees’ comfort and productivity. The type of establishment (fast food, casual, etc.) and climatic zone can influence thermal conditions in the kitchens. Moreover, the size and arrangement of the kitchen zones, appliances, etc., further complicate an evaluation of the indoor thermal environment in commercial kitchens. In general, comfort criteria are stipulated in international standards (e.g., ASHRAE 55 or ISO EN 7730), but are these standardized methods applicable to such environments as commercial kitchens? This article describes a data collection protocol based on measurements of physical and subjective parameters. The procedure was used to investigate more than 100 commercial kitchens in the United States in both summer and winter. The physical measurements revealed that there is a large range of kitchens environments and confirmed that employees are exposed to a warm-to-hot environment. The measured ranges of activities and temperatures in many cases were outside the range recommended by ASHRAE 55 and ISO EN 7730. The study showed that the predicted mean vote/percentage people dissatisfied (PMV/PPD) index is not directly appropriate for all thermal conditions in commercial kitchens.