Little research has focused on brief and practical strategies for addressing environmental tobacco smoke exposure through interventions focused explicitly on creating a smoke-free home. We used a two-group (intervention and control groups) repeated-measures randomized controlled trial design. Families were randomized to the intervention (n = 176) or control (n = 176) condition after the baseline interview, with outcome assessments for reported and urine cotinine measures at 2 (post-intervention), 6 (follow-up) and 12 (follow-up) months. Baseline urinary cotinine levels of both groups were not statistically significantly different (P > 0.05); however, post-intervention urinary cotinine levels were significantly different at 2, 6 and 12 months after start of the study (P < 0.001). As a physician-based brief intervention, our intervention was effective. Clinical providers might offer feedback and brief interventions to preteens and adolescents. Because of the ease of intervention on delivery, this intervention has the potential to have significant impact if widely disseminated.