This article examines the relationship between problem gambling, mental health, and criminal behavior in a sample of incarcerated Canadian male federal offenders (N = 254). In particular, the study compared correlates of problem gambling in the offender population with the correlates of problem gambling in a nonoffender population from a previous study. The offenders were assessed using self-report tests, interviews, and a file review. Of these offenders, 106 were interviewed in more depth. Results indicated that problem gambling was significantly correlated with social anxiety, depression, substance abuse, impulsiveness, and current and childhood attention-deficit/hyperactivity disorder (ADHD) symptoms. In addition, the results indicated that the correlates of problem gambling were similar in offender and nonoffender populations. The relationship of gambling problems to depression, anxiety, substance abuse, ADHD, and impulsiveness suggests that any intervention for this population needs to be comprehensive and take into consideration a broad range of clinical needs.