Background and aims Veterans who have recently left the military (i.e., transitioned) may be vulnerable to the development of psychiatric disorders, but little is known about gambling problems in this population. This study investigated the prevalence and risk factors of gambling problems, help-seeking amongst veterans with gambling problems, and relationships with trauma and posttraumatic psychopathology. Methods Cross-sectional self-report survey data from 3,511 Australian Defence Force members who left the military within the past five years. Surveys included measures of gambling problems (PGSI); depressive symptoms (PHQ-9); posttraumatic stress disorder (PCL-5); help-seeking behaviours; military and non-military-related trauma. Results Prevalence rates for problem gambling (PGSI ≥ 5) were 4.6%, while an additional 8.8% were classified in terms of at-risk gambling (PGSI = 1–4). Time since leaving the military was not associated with gambling problems. Only 2.1% of veterans with problem gambling reported help-seeking for their gambling. While trauma exposure, depression, and Posttraumatic Stress Disorder (PTSD) were all related to gambling problems at the bivariate level, only arousal and dysphoric-related affect were uniquely associated with gambling problems when adjusting for covariates. Discussion Gambling problems may be under-recognised relative to other psychiatric issues. Posttraumatic mental health problems, rather than trauma exposure per se, may explain the relationship between trauma and gambling problems. Conclusions Some veterans are in a period of vulnerability during transition out of military service, and harms associated with gambling problems may be exacerbated during this period.