Background: Boarding students face unique challenges when entering school, including: adapting to a novel environment, where they are separated from family, friends and culture, for up to 40 weeks per year. A particular challenge is sleep. A further challenge is coping with the demands of boarding with its potential impact on psychological well-being. Aims: To explore how boarders' sleep differs from that of their day-student peers, and how this relates to psychological well-being. Sample and Methods: 309 students (59 boarding students and 250 day-students, at one Adelaide school) completed the School Sleep Habits Survey, Depression-Anxiety-Stress-Scale-21 (DASS-21), and Flourishing Scale. Boarding students additionally completed the Utrecht Homesickness Scale. Thirteen boarding students described experiences of sleeping in boarding through focus groups. Results: Boarding students, compared to day-students reported 40 minutes more sleep per weeknight (p < 0.001), with earlier sleep onset (p = 0.026), and later wake-up (p = 0.008) times. No significant differences were observed between boarding' and day-students' DASS-21 scores. Hierarchical regression revealed longer total weekday sleep time predicted higher psychological well-being in both boarding and day-students. Additionally, in boarding students, low homesickness-loneliness and homesickness-ruminations further predicted psychological well-being. Thematic analysis of boarding students' focus group responses revealed that night-time routine, and restricting technology use at night facilitated sleep. Conclusions: This study supports -- in both boarding and day-students -- the importance of sleep for adolescent well-being. Sleep hygiene can play an important role in boarding student sleep, especially: regular night-time routine and restricting technology use at night. Finally, these findings suggest that poor sleep and homesickness have an adverse effect on boarding student psychological well-being. This study highlights the importance of strategies which promote sleep hygiene and minimize homesickness, in boarding school students.