This study examined the impact of co-occurring Axis I disorders on drug treatment outcomes of drug-dependent pregnant women. Participants (N = 106) were women who met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for opioid dependence and were receiving methadone. Based on DSM-IV Axis I criteria, participants were categorized into three groups: (1) absence of mood/anxiety disorder (ND, n = 29), (2) primary mood disorder (MD, n = 39), or (3) primary anxiety disorder (AD, n = 38). Demographically, the groups were similar. The MD group was significantly more likely to be positive for drugs while in treatment compared with both the ND and AD groups. The MD and AD groups had more psychosocial impairment and higher incidence of suicidal ideation compared with the ND group. Interestingly, the AD group spent more days in treatment compared with the ND or MD group. These findings highlight the need to treat co-occurring Axis I disorders, particularly given the higher relapse risk for those with mood disorders.