Mothers with problematic substance use often experience complex mental health challenges. However, an examination of mental health is often limited to depression despite increased occurrence of trauma in this population. Study one described depressive symptoms, trauma, emotion regulation, and their interrelations in 12 mothers participating in a parenting intervention as part of their substance use treatment. Mothers presented with median depressive and PTSD symptom scores within the clinical range. A preference for soothing was greater among mothers with higher PTSD symptoms. Study two examined the relationship between mental health and parenting intervention engagement. Time between early intervention sessions was positively correlated with PTSD avoidance symptoms and enhancing positive affect and negatively related to social modeling. These findings underscore investigating mental health beyond depression and suggest that trauma and emotion regulation may be particularly important when considering the impact of mental health on parenting intervention engagement within substance use treatment.