Purpose: This study aims to determine the effect of online social networks on university students' environmentally responsible behavior (ERB). This research aimed to develop and test a behavioral model in the context of online social networks, where students' attitudes, knowledge and behavior influence their ERB. Design/methodology/approach: This study used a quasi-experiment with a pretest-posttest design and a random parallelization control group. The research used a questionnaire to assess ERB, environmental attitudes and environmental knowledge. The researcher randomly assigned 120 students to an experimental and a control group of equal size. Both groups initially completed a pretest. The experimental group was trained in environmental issues over four months (an academic semester) via an online social network. Findings: The findings indicated that the social network had a significant effect on motivating ERB. Additionally, it improved environmental attitudes. According to the results, online social networks such as Facebook can significantly aid in teaching and learning environmental issues in formal academic settings. Originality/value: Online social networks facilitated significant cognitive progress in environmental education. The primary objective is to educate students about ERB.