Résumé : Background: Although previous studies have reported the efficacy of communication skills training (CST) programs, specific training addressing communication about uncertainty and hope in oncology has not yet been studied. This paper describes the study protocol of a randomized controlled trial assessing the efficacy of a CST program aimed at improving physician ability to communicate about uncertainty and hope in encounters with cancer patients. Methods/design: Physician participants will be randomly assigned in groups (n = 3/group) to a 30-h CST program (experimental group) or to a waiting list (control group). The training program will include learner-centered, skills-focused, practice-oriented techniques. Training efficacy is assessed in the context of an encounter with a simulated advanced stage cancer patient at baseline and after the CST for the experimental group, and after four months for the waiting-list group. Efficacy assessments will include communicational, psychological and physiological measures. Group-by-time effects will be analyzed using a generalized estimating equation (GEE). A power analysis indicated that a sample size of 60 (30 experimental and 30 control) participants will be sufficient to detect effects. Discussion: The current study will aid in the development of effective CST programs to improve physician ability to communicate about uncertainty and hope in encounters with cancer patients. Trial registration: US Clinical Trials Register NCT02836197.