This study explores how climatic background or long-term thermal history influences individuals’ in-the-moment thermal comfort experiences. This investigation was conducted at eight mixed-mode university buildings in United Kingdom whose occupants had diverse thermal histories. The research design consisted of simultaneous environmental measurements, a questionnaire survey and observation on 3,452 students performing sedentary activities in the classrooms. To eliminate the influence of acclimatisation in the UK, a subset of 1,225 students with less than 3 years of residence in the UK were selected as the survey sample. Students’ thermal comfort responses were categorised into three main groups based on their climatic background compared to the UK (warmer, similar and cooler climatic background groups). Data was statistically analysed to derive the thermal comfort requirements of each climatic group based on reported thermal sensations, preferences, acceptability and comfort votes. The findings confirm the influence of long-term thermal history on thermal sensation, thermal comfort zone, acceptability, preference and comfort temperature (neutrality). There was generally no difference in the subjective thermal comfort of the students with similar climatic backgrounds to the UK and those from cooler climates than the UK. However, significant differences appeared between the warmer thermal history group and the other two groups. It was also demonstrated that the participants with a warmer thermal history had cooler thermal sensations compared to their counterparts in the similar-to and colder-than-UK thermal history groups, when exposed to the same environments. The optimal acceptable temperature was higher for the warmer climatic background (24 °C) than the similar/cooler climatic background groups (22 °C). Likewise, heightened values of preference and comfort temperatures were observed for the warmer thermal history group than the other two groups, despite their heavier clothing insulation than the other groups.