Background: Observation of performance followed by feedback is the key to good teaching of communication skills in clinical practice. The fact that it occurs rarely is probably due to clinical supervisors' perceived lack of competence to identify communication skills and give effective feedback. We evaluated the impact of a faculty development programme on communication skills teaching on clinical supervisors' ability to identify residents' good and poor communication skills and to discuss them interactively during feedback. Methods. We conducted a pre-post controlled study in which clinical supervisors took part to a faculty development program on teaching communication skills in clinical practice. Outcome measures were the number and type of residents' communication skills identified by supervisors in three videotaped simulated resident-patient encounters and the number and type of communication skills discussed interactively with residents during three feedback sessions. Results: 48 clinical supervisors (28 intervention group; 20 control group) participated. After the intervention, the number and type of communication skills identified did not differ between both groups. There was substantial heterogeneity in the number and type of communication skills identified. However, trained participants engaged in interactive discussions with residents on a significantly higher number of communication items (effect sizes 0.53 to 1.77); communication skills items discussed interactively included both structural and patient-centered elements that were considered important to be observed by expert teachers. Conclusions: The faculty development programme did not increase the number of communication skills recognised by supervisors but was effective in increasing the number of communication issues discussed interactively in feedback sessions. Further research should explore the respective impact of accurate identification of communication skills and effective teaching skills on achieving more effective communication skills teaching in clinical practice.