Abstract Objective Patients’ unhealthy alcohol use is often undetected in primary care. Our objective was to examine whether physicians’ attitudes and their perceived self-efficacy for screening and counseling patients is associated with physicians’ counseling of patients with unhealthy alcohol use, and patients’ subsequent drinking. Methods This study is a prospective cohort study (nested within a randomized trial) involving 41 primary care physicians and 301 of their patients, all of whom had unhealthy alcohol use. Independent variables were physicians’ attitudes toward unhealthy substance use and self-efficacy for screening and counseling. Outcomes were patients’ reports of physicians’ counseling about unhealthy alcohol use immediately after a physician visit, and patients’ drinking six months later. Results Neither physicians’ attitudes nor self-efficacy had any impact on physicians’ counseling, but greater perceived self-efficacy in screening, assessing and intervening with patients was associated with more drinking by patients six months later. Conclusions Future research needs to further explore the relationship between physicians’ attitudes towards unhealthy alcohol use, their self-efficacy for screening and counseling and patients’ drinking outcomes, given our unexpected findings.