Nowadays, when local and global environmental problems are increasing, it is seen that human activities mainly cause environmental problems. Undoubtedly, the most effective way to solve these problems is environmental education, which aims to raise people's awareness. Within the scope of the study, the aim was to raise students' awareness about biodiversity by using the PBL method. In the 7th grade "Human and Environmental Relations" unit, the case study design, one of the qualitative research designs, was used to determine the effect of problem-based learning activities on students' understanding of biodiversity and its importance. Ten 7th-grade students participated in the study. The data of the study were obtained from the answers given by the students to the semi-structured interview questions in the fourth and fifth sections of the Environmental Awareness Interview Form. Content analysis was used to analyze the research data. As a result of the research, it was observed that the experimental group students, in which problem-based learning activities were carried out, had a higher awareness of not only interspecies biodiversity but also intraspecies biodiversity compared to the control group. In addition, it was determined that the experimental group students could evaluate the effects of the decrease in species diversity from multiple perspectives. In contrast, the control group students' perspectives on the subject were more limited. According to these results, deeper learning occurred in the experimental group students than in the control group.