Relationships between multiple sleep outcomes, obesity and adiposity across childhood and adolescence have been previously reported. Health-promoting interventions to improve sleep and reduce adolescent obesity could target shared determinants of sleep and obesity. The aim of this systematic review was to systematically identify and examine research that investigated the shared determinants of poor sleep and increased adiposity or obesity in adolescents. A systematic literature search covering publications up to April 2024 was conducted across 10 bibliographic databases. Search terms included objective and subjective sleep/circadian rhythm measurements, objective adiposity measurements and adolescents aged 8-18 years. Eighty studies were included in the final review. Determinants were categorised into three different domains: socioenvironmental determinants, behavioural determinants and health determinants. Shared determinants of poor sleep and increased adiposity or obesity in adolescents aged 8-18 years included: socioenvironmental determinants (gender, ethnicity, pubertal status, academic attainment), behavioural determinants (timing of moderate-to-vigorous physical activity (MVPA), unhealthy diet choices and timing of consumption and screen time and videogaming quantity and timing) and health determinants (wellbeing). These findings suggest that sleep hygiene and the modifiable shared behavioural determinants should be targeted in health-promoting interventions, and statistical analyses should be adjusted for socioenvironmental determinants and wellbeing.