Purpose Sleep disturbance is a common difficulty in the general population. It has become particularly prevalent in the context of disruption to routine brought about by the COVID-19 pandemic. The purpose of this study was to trial a patient-guided “sleep workbook” intervention, which was developed by multidisciplinary team members, combining principles of sleep hygiene education and cognitive behavioural therapy for insomnia behavioural strategies, and to evaluate its efficacy in a mixed-methods study. Design/methodology/approach Service users of the community mental health service were invited to participate. A total of 30 service users agreed to participate. A total of 15 participants completed both the intervention and the mixed-methods survey. Four participated in the focus group. Descriptive and inferential statistics were performed on the collected quantitative data. A thematic analysis was carried out of qualitative survey responses and focus group discourse. Findings There was a statistically and clinically significant improvement in quantity and quality of sleep following intervention. Mean hours of sleep prior to the intervention was 4.4 hours [standard deviation (SD) = 2.2], compared to 6.1 hours (SD = 2.2) afterwards (p = 0.003). Quality of sleep improved from a mean of 2.5 (SD = 2.1) to 6.1 (SD = 2.3) following the intervention (p = <0.001). Four themes were developed using the qualitative data: “under-recognition of sleep difficulties”, “ruminations”, “practical utility” and “therapeutic autonomy”. Originality/value There is a growing need for occupational therapists and clinicians to provide interventions for patients with sleep difficulties and to develop sleep management practice. This patient-guided sleep workbook may be an effective intervention for these patients.