This study aimed to explore the familiarity with and opinions toward Education for Sustainable Development (ESD) among Montenegrin students at the end of their basic school years and upon entering upper-secondary school. The participants of the study were gathered in 2022, and the data were recorded via an online survey platform. The results were obtained from 705 students in the first grade of upper-secondary school. The results indicate a notable lack of student familiarity with the content of the ESD curriculum, despite it being a compulsory part of the basic school since 2014. The content listed in the curriculum of ESD for basic school is only sporadically or rarely integrated into teaching practice. Respondents mostly showed a neutral opinion toward the ESD content and its implementation practices. They did not demonstrate a clear majority opinion toward embracing sustainable thinking and behavior. Based on the study findings, there is an urgent need for comprehensive teacher training in all subjects for basic school teachers. The study recommends developing effective assessment tools for ESD concepts, providing teaching materials, and appropriate literature to integrate ESD content into each subject, ensuring the competent achievement of ESD goals.