Introduction <p>In France, chronic insomnia affects 15.8% of the general population. It is frequently observed among people with psychiatric disorders, and significantly impacts clinical outcomes, treatment responses, functional abilities, quality of life, and sleep medication use. In France, public outpatient psychiatric services represent the main access point to psychiatric care. However, to date, we found no study that explored the prevalence of insomnia among patients receiving care in these settings. This study aimed to estimate the prevalence of insomnia in outpatient public psychiatric services and to describe associated factors and current care management.</p> Method <p>We conducted a monocentric, descriptive, cross-sectional study using a patient questionnaire and a pseudo-random sampling method. All adult patients getting care appointment on January 18, 2024, in the Community Mental Health Centers, Community-Based Rehabilitation Centers, and Psychiatric Day Hospitals affiliated with the Guillaume Régnier Psychiatric Hospital in Rennes, France, were eligible. Insomnia was assessed using the Insomnia Severity Index (score of ≥ 15 indicating clinical insomnia). Sociodemographic, clinical, comorbidity, and sleep hygiene data were collected through the questionnaire and compared between patients with and without insomnia via logistic regression.</p> Results <p>Out of 624 eligible individuals, 511 completed the survey (participation rate: 81.9%). The prevalence of clinical insomnia was 34.8%. In multivariate analysis, higher education level (A-Level: Odds Ratio 2.11, <i>p</i> = 0.019; Post-A-Level: OR 2.06, <i>p</i> = 0.007), depressive disorders (OR 2.16, <i>p</i> = 0.039), nighttime exposure to light/noise (OR 1.82, <i>p</i> = 0.013), and screen use before bedtime (OR 1.90, <i>p</i> = 0.021) were significantly associated with a higher probability of having insomnia, conversely to financial stability (It’s all right: OR 0.38, <i>p</i> = 7.1^E − 4; It’s tigh: OR 0.40, <i>p</i> = 0.003) and regular sleep schedules (OR 0.25, <i>p</i> = 2.1^E − 9) significantly associated with a lower probability. The main care management was sleep medication (61.2% of those with insomnia vs. 45.3% without). Non-pharmacological approaches such as CBT-I (4.5%), and sleep hygiene education groups (3.7%) were infrequently used.</p> Conclusion <p>This study reveals the high prevalence of clinical insomnia among individuals receiving outpatient psychiatric care. It highlights specific risk factors and underlines the predominance of pharmacological care management, raising concerns about iatrogenic effects. There is a need to develop accessible and adapted non-pharmacological treatments.</p> Clinical trial number <p>Not applicable.</p>