The aim of this study was to investigate the nature of collaborative argumentation by students enrolled in a degree program in social services. Students (n = 29) in a University of Applied Sciences participated in role-play discussions and problem solving on adolescents’ substance abuse. The discussions were conducted either online (15 students) or face-to-face (14 students). The data comprise the students’ asynchronous online and face-to-face discussions, which were analysed by identifying discussion fragments relevant in collaborative argumentation, and by comparing the results of the two groups. The results showed that the face-to-face discussions were more collaborative than the online discussions. Collaboration during the face-to-face interaction was particularly evident in the higher number of explanations and acceptances. The online discussions, in turn, exhibited a higher quality of argumentation than the face-to-face discussions. However, the level of students’ justifications in both discussion types was rather low. In conclusion, these results emphasise the importance of developing methods of learning collaborative argumentation in social work education for students’ multifaceted understanding of issues encountered in the field.