There is a paucity of research on the efficacy of online asynchronous discussion forums in fostering critical thinking, social justice awareness and empathy in pre-service teachers. This study adopted a case study design rooted in the social constructivist/interpretive paradigm. South African university pre-service teachers comprised the study’s sample. To examine how online discussions about Global Citizenship Education (GCE) affected the critical thinking and social justice awareness of a group of pre-service teachers ( n = 31), a questionnaire based on Andreotti’s (2006) Soft vs Critical GCE framework was used. To further understand how their involvement in online discussions on global issues influenced their sense of social justice awareness, empathy and critical thinking, certain pre-service teachers’ ( n = 9) reflective essays were used. The findings revealed that pre-service teachers’ responses were more consistent with the soft GCE approach. The Soft vs Critical GCE framework was useful for identifying which aspects of online interactions require a more critical understanding of GCE. The findings showed that pre-service teachers who participated in the online GCE conversations had increased social justice awareness, critical thinking skills and empathy.