OBJECTIVE: Sleep problems are a major risk factor for the emergence of mental health problems in adolescence. The aim of this study was to investigate the post intervention effects of a cognitive-behavioral/mindfulness-based group sleep intervention on sleep and mental health among at-risk adolescents. METHOD: A randomized controlled trial (RCT) was conducted across High schools in Melbourne, Australia. One hundred forty-four adolescents (aged 12-17 years) with high levels of anxiety and sleeping difficulties, but without past or current depressive disorder, were randomized into either a sleep improvement intervention or an active control 'study skills' intervention. Both programs consisted of 7 90-min-long group sessions delivered over 7 weeks. One hundred twenty-three participants began the interventions (female = 60%; mean age = 14.48, SD = 0.95), with 60 in the sleep condition and 63 in the control condition. All participants were required to complete a battery of mood and sleep questionnaires, 7 days of wrist actigraphy (an objective measure of sleep), and sleep diary entry at pre- and-post intervention. RESULTS: The sleep intervention condition was associated with significantly greater improvements in subjective sleep (global sleep quality [with a medium effect size], sleep onset latency, daytime sleepiness [with small effect sizes]), objective sleep (sleep onset latency [with a medium effect size]), and anxiety (with a small effect size) compared with the control intervention condition. CONCLUSION: The SENSE study provides evidence that a multicomponent group sleep intervention that includes cognitive-behavioral and mindfulness-based therapies can reduce sleep initiation problems and related daytime dysfunction, along with concomitant anxiety symptoms, among at-risk adolescents. (PsycINFO Database Record