Poor sleep quality is prevalent among members of the military but rates of poor sleep quality vary between studies. This study examined the global prevalence of poor sleep quality in military personnel and veterans as well as possible moderators of prevalence differences between studies. PubMed, EMBASE, Web of Science, and PsycINFO were systematically searched from their inception dates to September 1, 2022. Studies were included if they were conducted on military personnel and/or veterans and prevalence estimates of poor sleep quality could be generated from assessments with standardized tools. A random-effects model was used to calculate the pooled prevalence and its 95% confidence intervals (CIs). Fifty-nine studies (N = 28,100) were included for analysis with sample sizes ranging from 14 to 8481. Two studies were rated as “high quality” (3.39%), while 57 were rated as “moderate quality” (96.61%). The overall pooled prevalence of poor sleep quality in military personnel and veterans was 69.00% (95% CI: 62.33–75.30%); pooled rates were 57.79% (95% CI: 49.88–65.50%) and 82.88% (95% CI: 74.08–90.21%) for active duty personnel and veterans, respectively. Subgroup analyses indicated study region, study design, sampling method, Pittsburg Sleep Quality Index cut-off values, and service type moderated prevalence of poor sleep quality. Meta-regression analyses indicated sample size, mean age, depression and posttraumatic stress disorder (PTSD) were associated with prevalence differences between studies. Poor sleep quality was more common in both active duty military personnel and veterans who were older and those who reported PTSD or depression. Regular monitoring of sleep quality and sleep hygiene should be promoted in this population. More relevant studies in middle- and low-income countries should also be conducted.