Individuals seeking substance use treatment who have one or more co-occurring mental health problems tend to have lower treatment engagement, higher rates of attrition, and poorer treatment outcomes. Readiness to change (RTC) is an integral construct in the recovery process, with higher RTC associated with improved treatment outcomes. However, the impact of psychiatric symptoms on RTC is not fully understood, especially among specialty subpopulations, such as military Veterans. Therefore, the aim of the present study was to examine the associations of mental health problems with RTC in a sample of Veterans initiating outpatient substance use treatment. The present sample was comprised of 278 Veterans (12% women, M = 48.22, SD = 14.06) who completed self-report intake measures assessing past month substance use frequency, substance-related consequences, symptoms of insomnia, depression, and anxiety, and importance and confidence to change one's substance use. Four separate canonical correlation analyses focusing on RTC alcohol, opioid, cannabis, and nicotine use were conducted. Veterans' inclusion in each analysis was not mutually exclusive. Results indicated that greater depression, anxiety, consequences, and frequency of alcohol use corresponded with greater importance to change alcohol use. Likewise, greater depression, anxiety, and insomnia symptoms along with frequency of use and consequences related to greater importance and confidence to change one's opioid use. In contrast, greater anxiety, depression, insomnia, and frequency of use were associated with less confidence in one's ability to change cannabis use. None of these variables were related to one's RTC nicotine use. Findings highlight the importance of assessing mental health problems at outset of substance use treatment, as they may be an indication of RTC and could be used as a catalyst to advance Veterans forward in the process of behavior change.