The paper presents the results of empirical research on the effectiveness of online discussions (OD) as a tool for forming argumentation skills among technical university students. On the one hand the actuality of the research is conditioned by the significance of discussion-based training of modern technical specialists under conditions of networking and socio-technical transformation of engineering activity. On the other hand, this problem is not elaborated in the domestic, pedagogies and also contradictory and poorly studied aspects in the foreign one. The results of the present study are important for scientifically substantiated methodological implementation of new approaches to engineering training under conditions of digitalization of education and increased requirements for discussion and information competence of a modern technical specialist. The research was conducted on the basis of two Novosibirsk universities and covered 350 second – and third-year students in "construction" and "automation and computer engineering" baccalaureate specialties. The analysis of the OD results conducted in VLE "Moodle" using "debate" (synchronous discussion) and "forum" (asynchronous discussion) methods showed that inclusion of online-discussions in to the educational process of technical universities improves argumentation skills of future engineers by 20-30 %. The data obtained at the stages of the forming and control experiment let us reveal a higher efficiency of asynchronous forms of online-discussions in comparison with synchronous ones. Their advantage is to 28,68 %, depending on the formed component of argumentation. Based on the results of the study recommendations were given to teachers to improve the effectiveness of social interaction of students during OD, including the feasibility of replacing debates with synchronous discussion methods, more focused on the joint search for solutions.