This study investigated the effectiveness of the orientation, identify, discussion, decision, and engage in behavior (OIDDE) learning model in enhancing biology learning outcomes, critical thinking, ethical attitudes, and engagement among high school students in Indonesia. Employing a quasi-experimental design with pre- and post-tests, the research included 66 randomly sampled students, evenly divided into experimental and control groups. Data were gathered through validated observation sheets, ethical attitude questionnaires, and tests, with analysis of covariance (ANCOVA) analysis conducted following normality and homogeneity tests. Results indicated significant improvements across all measured variables in the experimental group compared to the control group. The findings suggest that the OIDDE model was more effective than conventional methods in fostering comprehensive educational outcomes in biology, as its problem-based approach promotes active learning, ethical decision-making, and collaborative problem-solving, aligning well with the needs of 21st-century education. This study underscores the model's potential for broader application across various subjects to enhance critical thinking, ethical behavior, and sustained student engagement.