Although co‐occurring posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) is associated with greater distress, impairment, and health care utilization than PTSD alone, the magnitude of this problem is uncertain. This meta‐analysis aimed to estimate the mean prevalence of current MDD co‐occurrence among individuals with PTSD and examine potential moderating variables (U.S. nationality, gender, trauma type, military service, referral type) that may influence the rate of PTSD and MDD co‐occurrence. Meta‐analytic findings (k = 57 studies; N = 6,670 participants) revealed that 52%, 95% confidence interval [48, 56], of individuals with current PTSD had co‐occurring MDD. When outliers were removed, military samples and interpersonal traumas demonstrated higher rates of MDD among individuals with PTSD than civilian samples and natural disasters, respectively. U.S. nationality, gender, and referral type did not significantly account for differences in co‐occurrence rates. This high co‐occurrence rate accentuates the importance of routinely assessing MDD among individuals with PTSD and continuing research into the association between these disorders.