Introduction: Verbal and non-verbal communication skills are core competencies in medical practice and should be acquired and monitored in medical schools. However, their assessment poses a challenge. The aim of this study is to develop and assess the psychometric properties, validity and reliability of a communication assessment scale.Material and Methods: We developed a communication assessment scale, composed by five dimensions (Structure, Way of Questioning, Behavior and Posture, Clarity of information and Emotional dimension). Two focus groups and a development group, composed by faculty members and standardized patients experienced in assessment, were responsible for creating the scale.Results: The communication assessment scale was tested on 332 students from the 3rd and 6th year of medical school, with a total of 2754 assessments, performed by faculty members and standardized patients. A descriptive analysis, an exploratory factor analysis, a confirmatory factor analysis and a Cronbach’s alpha analysis to establish internal reliability were conducted.Discussion: The Minho Communication Assessment Scale can be effectively used by both faculty members and standardized patients, providing correct students assessment and relevant feedback to the students. The final Minho Communication Assessment Scale has a total of 19 items, being simple and intuitive to use. The exploratory factor analysis and confirmatory factor analysis results were satisfactory. Cronbach’s alpha value revealed high internal consistency of Minho Communication Assessment Scale.Conclusion: The final Minho Communication Assessment Scale proved to be simple to use and to have very good psychometric properties. Our results show that the Minho Communication Assessment Scale is a valid scale to assess communication skills which can be accurately replicated on objective structured clinical examinations focusing on communication.