Objectives: In light of the high prevalence of sleep disorders in patients suffering from posttraumatic stress disorder (PTSD), this study sought to compare the effect of prazosin and hydroxyzine on sleep quality in this patient group. Methods: A total of 100 patients suffering from PTSD were assessed (mean age = 35.51 years, SD = 6.41; 28% females). Next, they were randomly assigned to one of three treatment groups: prazosin (33 patients), hydroxyzine (34 patients) or placebo (33 patients). The trial lasted for 8 weeks. The patients' sleep quality was assessed using the Pittsburgh Sleep Quality Index. Items taken from the Mini International Neuropsychiatric Interview were used to operationalize PTSD. Results: Compared to controls, patients treated with prazosin and hydroxyzine reported improved sleep and less nightmares. Improvement was greatest in patients treated with prazosin compared to hydroxyzine and placebo. Improvement in sleep was associated with an amelioration of their PTSD symptoms. Conclusion: Both prazosin and hydroxyzine can be used to treat psychopharmacological sleep disorders and nightmares in patients suffering from PTSD, also leading to reductions in PTSD symptoms.