There is considerable public and professional concern about the mental health status of veterans deployed to Iraq and Afghanistan as well as how to engage and retain symptomatic veterans in treatment. This study examined demographic, psychiatric, and psychosocial determinants of prospective initiation and retention in mental health services among symptomatic Iraq/Afghanistan veterans. One hundred thirty-seven symptomatic veterans who were referred to mental health screening completed a survey at the time of their first mental health visit. Associations between survey variables and subsequent Veterans Affairs service utilization were evaluated. The most consistent determinants of mental health service initiation and retention were severity of posttraumatic stress disorder (PTSD) and depressive symptoms. Notably, whereas PTSD-related re-experiencing symptoms were independently associated with initiation of mental health treatment, PTSD-related numbing symptoms were independently associated with retention in treatment. Stigma, barriers to care, and beliefs about mental health treatment were not associated with either mental health initiation or retention.