The thermal comfort experienced during sleep onset latency (SOL) significantly influences overall sleep quality. While most previous studies have primarily focused on thermal comfort during actual sleep, this study aims to investigate and compare the bed microclimate and thermal comfort during SOL in school-aged children and adults, taking into account their differing physiological characteristics and thermal preferences under various sleep thermal conditions. Fourteen school-aged children and fourteen adults participated in two experiments conducted under winter conditions (8 °C and 11 °C), as well as two experiments under transitional conditions (21 °C and 24 °C). Each experiment lasted 60 min, with continuous monitoring of skin temperatures and bed microclimate throughout the duration. Subjective assessments of thermal perception were collected after each experiment. The experimental results indicate that the difference in skin temperature (T