Characterising sleep in young people (aged 15–25 years) with borderline personality disorder (BPD) features is crucial given the association between BPD features and sleep disturbance, negative consequences of poor sleep, and normative developmental sleep changes that occur in this age group. The present study aimed to characterise the sleep profile of young people with BPD to determine whether this profile is non-normative and specific to BPD. Participants were 96 young people (40 with BPD features, 38 healthy individuals, and 18 young people seeking help for mental health difficulties without BPD). Sleep was measured subjectively (self-report questionnaires) and objectively (10 days of actigraphy). Young people with BPD features reported poorer subjective sleep quality, greater insomnia symptoms and later chronotype than same-age healthy and clinical comparison groups. Young people with BPD features also displayed irregular sleep timing, later rise times, greater time in bed and longer sleep durations than healthy young people. Those with BPD features had superior sleep quality (greater sleep efficiency, less wake after sleep onset) and longer sleep durations than the clinical comparison group. Sleep profiles were similar across young people with BPD features with and without co-occurring depression. Overall, the findings revealed a subjective–objective sleep discrepancy and suggest that sleep-improvement interventions might be beneficial to improve subjective sleep in young people with BPD features.