Mobile phone use is often blamed for adolescent sleeping difficulties in the popular and scientific literature, with correlations observed between adolescents' mobile phone use and their bedtime. We aimed to obtain experimental evidence to support these causal claims. A within-subjects experiment (baseline, intervention) was conducted in adolescents' homes, to determine the effect of restricting adolescents' pre-bed mobile phone use on school night sleep habits. Following a baseline week, adolescents were given individualized phone stop times, 1 hour before bed for one school week. An online sleep diary was used to monitor bedtime, lights out time, sleep latency and total sleep. Sixty three adolescents (age range 14-18, M = 16.3, SD = 0.93yrs; 17%male) provided data. During one week of phone restriction, adolescents stopped using their phones earlier (80 min, p < .001), turned their lights off earlier (17 min, p = .01), and slept longer (21 min, p = .01). Participant recruitment was low (26%), indicating many adolescents lack motivation to negotiate changes to their evening phone use. Overall, there are potential benefits of restricted mobile phone use during the pre-sleep period, yet, future research is needed to identify non-technological interventions to increase adherence to phone restriction (e.g., motivational interviewing) or otherwise decrease pre-sleep arousal (e.g., cognitive strategies).