PURPOSE: We tested whether an online intervention combined with a patient feedback report improved physicians' use of motivational interviewing (MI) techniques when discussing weight with overweight and obese adolescents. METHODS: We randomized 46 pediatricians and family physicians and audio recorded 527 patient encounters. Half of the physicians received an individually tailored, online intervention. Then, all physicians received a summary report detailing patient's weight-related behaviors. We coded MI techniques and used multilevel linear mixed-effects models to examine arm differences. We assessed patients' motivation to change and perceived empathy after encounter. RESULTS: We found arm differences in the Intervention Phase and the Summary Report Phase: Empathy (p < .001), MI Spirit (p < .001), open questions (p = .02), and MI consistent behaviors (p = .04). Across all three phases (Baseline, Intervention, and Summary Report), when physicians had higher Empathy scores, patients were more motivated to change diet (p = .03) and physical activity (p = .03). In addition, patients rated physicians as more empathic when physicians used more MI consistent techniques (p = .02). CONCLUSIONS: An individually tailored, online intervention coupled with a Summary Report improved physicians' use of MI, which improved the patient experience.