This study investigates the effectiveness of the Toulmin argumentation model in developing critical thinking skills and epistemological beliefs concerning the internet in an online educational setting, especially during the global coronavirus pandemic. The subject of the research was carried out in the "Child Development Department" of a state university with the participation of 68 volunteer students, mostly from Eastern and Southeastern Anatolia, aged between 19 and 25. It employed quasi-experimental design in the course of the ten weeks in the 2020-2021 academic years. Data were collected through online tests and evaluations during child science and technology lessons focusing on various spatial and contemporary scientific topics. Students' critical thinking skills and epistemological beliefs were according to predetermined scales, and were analyzed using SPSS 22. Differences between the control and experimental groups were not significant for critical thinking skills or epistemological beliefs. This suggests that the implementation of the Toulmin model in an online format did not have any significant effects on these areas. Further, a very weak correlation between epistemological beliefs and critical thinking skills emerged, indicating that these constructs can work independently in online learning contexts. The results stress the complexities behind promoting critical thinking and epistemological beliefs in online learning environments, making it imperative to involve new theory in the integration of argumentation models, such as that of Toulmin's, into online education. The study seems to offer valuable theoretical guidance to the teachers and curriculum developers to effectively embed critical thinking and epistemological understanding in the digital age of education. Future research will involve longer interventions, diverse samples, and innovative strategies of teaching to affect epistemological beliefs and create opportunities for critical thinking in digital learning spaces.