Science learning for prospective teachers requires instructional materials that can connect scientific concepts with real-life problems and local cultural contexts; however, learning materials that integrate STEM with the local wisdom of the Maluku Islands to strengthen the scientific literacy of elementary teacher education students remain limited. This study aimed to develop a STEM-based e-module integrating the local wisdom of the Maluku Islands and to determine its validity, practicality, and preliminary effectiveness in improving the scientific literacy of Elementary Teacher Education (PGSD) students. This study employed a Research and Development (R&D) approach using the ADDIE model, which consists of Analysis, Design, Development, Implementation, and Evaluation, with a one-group pretest–posttest design for the preliminary effectiveness trial. The product trial involved 41 fifth-semester students from Class E of the PGSD Study Program enrolled in the STEM Education course, while product validation involved six validators consisting of two subject-matter experts, two media experts, and two language experts. Data were collected through observation, needs analysis questionnaires, expert validation sheets, a 25-item student response questionnaire, and a 24-item scientific literacy test administered as pretests and posttests. The data were analyzed quantitatively using the Gregory Index, practicality percentages, the Wilcoxon signed-rank test, and N-Gain analysis based on the ideal maximum score. The results showed Gregory Index values of 0.86 for content, 0.92 for media, and 0.95 for language, all of which were categorized as very high. The e-module achieved a practicality score of 85.97%, indicating a very practical category. The mean scientific literacy score increased from 24.80 on the pretest to 69.21 on the posttest, representing an improvement of 44.41 points (Wilcoxon Z = −5.58, p < 0.001, r = 0.87), with a mean N-Gain of 0.59 in the medium category. These findings indicate that the STEM-based e-module integrating the local wisdom of the Maluku Islands is valid, practical, and demonstrates preliminary effectiveness in supporting the improvement of scientific literacy among the PGSD students in the trial class. The e-module can be used as contextual instructional material in STEM Education, while further research is recommended to involve comparison groups, broader samples, and parallel test forms to strengthen evidence of its effectiveness.