<![CDATA[This study developed a diagnostic assessment based Biology e-module on environmental change and examined its feasibility, attractiveness, and effectiveness in improving Grade X students’ environmental literacy. The study employed Research and Development (R&D) using the ADDIE model (Analysis, Design, Development, Implementation, and Evaluation). Participants were selected through cluster random sampling at SMAN 1 Bandar Lampung. Class X.2 served as the experimental class (n = 36) and Class X.1 as the control class (n = 36), while a limited trial involved 10 students from Class X.5. Environmental literacy was assessed through a multiple-choice test covering ecological knowledge and cognitive skills, an environmental-attitude questionnaire, and behavioral observation. The final expert-validation scores were 89% for content, 90% for media, 91% for language, and 89% for assessment, all categorized as highly feasible. Student responses reached 80% in the limited trial and 85% in the large-scale trial, while the teacher response was 85%. The experimental class’s test score increased from 44.44 to 85.97 (N-Gain = 0.76, high), whereas the control class increased from 41.11 to 77.78 (N-Gain = 0.63, moderate). The post-test difference was significant, p (0,001) < a (0.05), with Cohen’s d 1.02. Environmental attitude scores also increased more strongly in the experimental class (N-Gain = 0.49) than in the control class (N-Gain = 0.35), while behavioral observations increased from 83.28 to 85.01 in the experimental class and from 76.90 to 77.45 in the control class. These findings indicate that the developed e-module is feasible, attractive, and effective for supporting the measured components of students’ environmental literacy.]]>
