Use rates of cannabis, a substance associated with a host of comorbid physical and mental health concerns, continue to rise for military veterans. Despite this prevalence, descriptive patterns of use among veterans and research on treatment factors that predict cannabis outcomes are lacking. This study aimed to conduct a descriptive profile of veterans who endorse cannabis use, compare veterans endorsing cannabis use to those who do not endorse use, and investigate what factors (other substance use, psychiatric symptoms, and treatment outcomes) predicted return to cannabis use following residential treatment. The study was a secondary data analysis of a longitudinal sample of U.S. military veterans (N = 200, 193 males, Mage = 50.14, SD = 9) participating in residential substance use disorder treatment through a Veterans Affairs medical center. Interview, survey, and electronic health data were collected over 12 months. Analyses included descriptive and frequency statistics to identify patterns in cannabis use behaviors and motives, independent t-tests to examine differences between the cannabis-using group and non-using group, and a series of univariate logistic regressions to examine potential predictors for cannabis use after treatment discharge. Lifetime cannabis use was common among veterans (77.5%), and 29.5% reported use during the study. On average, veterans had made one quit attempt before treatment entry. Veterans who endorsed cannabis use consumed more alcohol in the past 30 days at baseline and reported less impulse control and less confidence in maintaining abstinence at discharge. Length of stay in the residential program and no diagnosis of Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV cannabis use disorder criteria predicted post-treatment cannabis use such that veterans who remained in the program longer were more likely to abstain from cannabis use following treatment, and those who did not meet DSM-IV cannabis use disorder criteria were more likely to use following treatment. Identification of relevant risk factors and treatment processes, such as impulse control, confidence in treatment, and length of stay in treatment, provides practical recommendations for future intervention efforts. This study calls for further examination of cannabis use outcomes among veterans, particularly those participating in substance use treatment.