More than two-thirds of individuals with PTSD report significant sleep difficulties that correlate positively with PTSD symptom severity. The aim of the study was to assess the impact of sleep disturbances on PTSD symptom severity and perceived health. Ninety-two volunteer treatment-seeking adults with PTSD were administered a Structured Clinical Interview for DSM-IV (SCID; First, Spitzer, Gibbon and William, 1996), and a series of questionnaires assessing PTSD symptom severity, perceived health, sleep, and alcohol use. Results from regression analyses revealed that sleep quality has an impact on PTSD symptom severity and perceived mental health, even when the effect of other potential confounding variables (sociodemographic data, trauma-related characteristics, psychiatric comorbidities, alcohol, and psychotropic medication use) is controlled for. The present study highlights the important influence sleep has on the severity of PTSD symptoms. Future studies could explore whether the addition of interventions focusing on sleep help optimize PTSD treatment.