Current research on the thermal environment of sleep is mainly concerned with the during-sleep air temperature. The effects of pre-sleep thermal environment on sleep quality and thermal comfort were investigated in this study by creating five different pre-sleep thermal conditions (20°C, 22°C, 23°C, 24°C, and 25°C) in winter. Four healthy male students slept in a dormitory with multiple physiological parameters monitored continuously. Subjects were asked to fill up a questionnaire to assess their subjective sleep quality and their evaluation of the thermal environment. As pre-sleep temperature increased, the sleep onset latency (SOL) decreased and then increased. The duration of slow-wave sleep (SWS) significantly increased from 20°C to 23°C and decreased from 23°C to 25°C. Sleep quality was best at a pre-sleep temperature of 23°C. The pre-sleep thermal neutral temperature was 20.78°C, slightly below 23°C. These results indicated that a warm pre-sleep environment led to low SOL and high SWS duration, but a hot environment before sleep has a detrimental effect on sleep. Only an appropriate increase in pre-sleep temperature within the thermal comfort range was beneficial for sleep.