Educators have theorized that interventions grounded in dual process theory (DPT) and script theory (ST) may improve the diagnostic reasoning process of physicians but little empirical evidence exists. In this quasi-experimental study, we assessed the impact of a clinical reasoning (CR) curriculum grounded in DPT and ST on medicine residents participating in one of three groups during a 6-month period: no, partial, or full intervention. Residents completed the diagnostic thinking inventory (DTI) at baseline and 6 months. At 6 months, participants also completed a post-survey assessing application of concepts to cases. There was a significant difference between groups in application of concepts (no intervention 1.6 (0.65) compared to partial 2.3 (0.81) and full 2.2 (0.91),  = 0.05), as well as describing cases in problem representation format (no intervention 1.2 (0.38) and partial 1.5 (0.55) compared to full 2.1 (0.93),  = 0.004). There was no significant difference in change in DTI scores (no intervention 7.0 (16.3), partial 8.8 (9.8), full 7.8 (12.0)). Residents who participated in a CR curriculum grounded in DPT and ST were effective in applying principles of CR in cases from their practice. To our knowledge, this is the first workplace-based CR educational intervention study showing differences in the reasoning process residents apply to patients.