This research aimed to gain the value of responsibility implicitly through activity-based values education tasks (ABVET) prepared in secondary school science lessons. The research was carried out with the embedded quasi-experimental design, one of the mixed research methods. The study group of the research consisted of 37 middle school students in total. Non-parametric tests were used to analyze the quantitative data obtained within the scope of the research and descriptive analysis was used in the analysis of qualitative data. The Dilemma Situations Form (DSF) developed by the researchers, activity documents, student and researcher diaries, and focus group interview form was used as data collection tools. Lessons were taught in the control group as curriculum in practice. In the experimental group, lessons were taught by the researchers with an enriched content and activity program aimed at gaining responsibility value. It was concluded that there was a significant difference in favor of the experimental group between the post-test scores of the experimental and control groups. It was concluded that ABVET was effective in gaining responsibility value to sixth grade students with the data obtained from the DSF, activity documents, student and researcher diaries and focus group interview form. This research shows which method, technique, and material can be preferred for values education in science courses included in education programs. Given the promising results of the current research, methods or techniques related to the constructivist approach such as the appropriate values education program, ABVET should be used for different science subjects, various courses, and grade levels in future studies.