Sleep disturbance is increasingly recognized as a critical determinant of physical and mental health. People experiencing homelessness (PEH) face environmental, structural, and psychosocial barriers that significantly impair restorative sleep. This mixed-methods cross-sectional study examined the magnitude of sleep disturbance and explored perceived barriers and facilitators to sleep among 55 adults receiving street medicine services in Fresno, California. Sleep disturbance was measured using a modified PROMIS Sleep Disturbance Short Form, and qualitative responses were analyzed using inductive thematic analysis. The mean PROMIS T-score was 64.26 (SD = 8.38), exceeding the population norm of 50.Environmental exposure, lack of safety, chronic health conditions, and encampment sweeps were primary contributors to poor sleep. Findings highlight sleep instability as both a consequence and perpetuator of homelessness-related health disparities.