Background. This study presents findings on the effect of an office- based obstetrics training program (given the acronym OBIWOM) on substance use assessment, management, and referral self-efficacy among obstetricians and staff of private, community-based obstetric practices. Methods. Participants were obstetricians and staff from 10 of 27 available community-based, private obstetric practices in the target areas, for a practice participation rate of 37%. This study used a delayed treatment design to compare self-efficacy between practice staff randomly assigned to an immediate or delayed intervention group. Results. Self-efficacy increased significantly after intervention from baseline to first follow-up for the immediate group, while no change was shown for the delayed (control) group. The impact of the intervention on self-efficacy was replicated in the assessment construct only after the intervention for the delayed group. Conclusion. This research shows that education and training can effectively improve self-efficacy in obstetricians and their staff in the management of substance use and pregnancy.