This paper investigates the relationship between the actual thermal comfort levels measured according to EN 16798-1 standard and the expected thermal comfort of attendees in five parish churches throughout 2018. This is carried out through statistical analysis of qualitative research based on questionnaire responses from church goers and quantitative research based on indoor measured data. This investigation includes the gathering of scientific data relating to temperature and relative humidity together with statistical data through thermal sensation surveys (TSSs). Thus, this study provides first-hand information about occupants’ diversities of thermal sensations and dynamic behaviour adaptations to the intricate environment within churches. Results determine that a significant correlation exists between the actual thermal comfort levels measured according to EN 16798-1 standard and the expected thermal comfort perceived by the church attendees in most of the parish churches under review. Analysis of the sources of discomfort and suggestions made by the occupants revealed that passive design measures contribute towards improved indoor thermal conditions, reduced energy demand and lower carbon emissions. This information provides assurance for optimised decision-making methods, used to generate accurate solutions for policy-makers, architects and engineers, with an understanding of practical applications of passive measures for places of worship. Moreover, the paper provides insight on indoor comfort levels in places of worship within a Mediterranean context, which is insufficiently addressed by scholars at a global level.