This is a report of post-treatment findings from a completed randomized pilot study testing the preliminary efficacy of the Mothers and Toddlers Program (MTP), a 12 week attachment-based individual parenting therapy for mothers enrolled in substance abuse treatment and caring for children ages birth to 36 months. Forty-seven mothers were randomized to MTP versus the Parent Education Program (PE), a comparison intervention providing individual case management and child guidance brochures. At post-treatment, MTP mothers demonstrated better reflective functioning in the Parent Development Interview, representational coherence and sensitivity, and caregiving behavior than PE mothers. Partial support was also found for proposed mechanisms of change in the MTP model. Together, preliminary findings suggest that attachment-based interventions may be more effective than traditional parent training for enhancing relationships between substance using women and their young children.