This paper presents a study that examines the effect of a graduate course titled “Selected topics in interpersonal communication skills” on the students’ interpersonal communication skills as part of their 21
st
century skills. Subject to the COVID-19 constraints, the course was taught online in the winter semester of 2021 to 46 students, who practiced in four groups. The students, who were studying at the Technion a science and technology research university for a research-oriented graduate degree in a science, technology, engineering, or mathematics (STEM) subject, attended synchronous bi-weekly 1-h lectures and 1-h practice sessions. The two research questions were as follows: (1) Did the interpersonal communication skills of the participants change following their participation in the course, and if so, how? (2) What was the effect of online learning on the students' interpersonal communication skills of (a) written and oral communication, (b) peer evaluation and feedback, and (c) self-reflection? Research tools included students’ self-presentations, questionnaires, peer assessments, and reflections during the course. Analyzing the data quantitatively and qualitatively, we found that the graduate students improved their interpersonal communication skills and benefited from exposure to a variety of knowledge and research fields, contributing to a sense of pride in their university affiliation. The students suggested adding a practical component on providing constructive feedback and rendering the course mandatory to all the graduate students in the university. The contribution of this research is the creation and favorable assessment of an online course that develops interpersonal communication skills among graduate students from a variety of STEM faculties.