It is the intent of this study to examine the relationship between the number of co-occurring disorders in a sample of pathological gamblers and variables associated with clinical presentation and treatment outcomes. Participants were given screening tools for four common psychological disorders: the hands depression screen, the Mood Disorder Questionnaire, the Carroll-Davidson generalized anxiety disorder screen, and the Sprint-4 PTSD Screen. The number of co-occurring disorders, as indicated by the results of these screening instruments, was compared to severity of gambling problems at outset of treatment, as measured by the NORC diagnostic screen for gambling problems-self administered. The number of co-occurring disorders was also compared to psychosocial functioning at the outset of treatment, as well as level of improvement in psychosocial functioning through treatment. Psychosocial functioning was measured using the Outcome Questionnaire 45 (OQ-45). The number of co-occurring disorders was compared to participant satisfaction with the therapeutic relationship as measured by the working alliance inventory-short form. Results suggest that co-occurring disorders are commonplace among treatment seeking pathological gamblers. Over 86 % of the sample screened positively for at least one of the four targeted psychological disorders. Furthermore, the number of co-occurring disorders was found to be positively related to severity of gambling problems at outset of treatment and negatively related to level of psychosocial functioning at outset of treatment. However, the number of co-occurring disorders was not found to be significantly related to level of improvement in psychosocial functioning through treatment. Overall, those that attended at least six sessions reported significantly improved psychosocial functioning by the end of their sixth session. Finally, the number of co-occurring disorders was not found to be significantly related to participants’ reported level of satisfaction with the therapeutic relationship.