The aim of this study is to increase pre-service science teachers' awareness of climate change through online argumentation activities. The study prepared pre-service training content based on online argumentation to increase climate change awareness. For the training, activities were prepared based on online argumentation for the sub-dimensions of climate change, which are content knowledge, awareness of the effects of climate change, awareness of personal initiatives, awareness of industrial initiatives, and tendencies towards preventing climate change. Expert opinions were taken about the activities and then they were finalized. Data was collected through an open-ended questionnaire applied as pre- and post-test. 32 pre-service science teachers from 22 different universities across Türkiye participated in the online training. The climate change awareness form was applied before and after the training. Data was analyzed using a content analysis approach. As a result of the study, it was observed that there was a significant difference in the pre-service teachers' content knowledge of climate change, and they provided more justifications in the sub-dimensions of climate change awareness after the training, and their awareness increased.