Interdisciplinary STEM education is a particular pedagogical methodology in which learners learn the association and connection of the knowledge of science and mathematics through particular technological engineering. To achieve this, specific interdisciplinary STEM-based educational curricula should be developed, and teachers should be qualified appropriately before any implementation process. Therefore, the aims of the research are both to (a) reveal the effect of the STEM workshop on science teachers' awareness of the relationship between science and other disciplines and to (b) examine its transferring contribution to their lesson planning approach. The case study method was used to get the essential data of research with 40 science teachers. The data were gathered via the Questionnaire for Interdisciplinary Association of Science, the lesson plans, and semi-structured interviews. As a result of the research, less variation is found in disciplines associated with science such as mathematics, technology-design, social studies, engineering, visual arts, Turkish languages, and music, etc. compared to data tools that they applied before and after workshop sessions. Besides, the post-applied data tool results revealed that the participants provided more comprehensive explanations regarding the direction of the interdisciplinary association, which suggests a better understanding of the relationship of science with other disciplines in the latter case. In addition, it was determined that most of the teachers designed their lesson plans based on an interdisciplinary approach and used the Engineering Design Process (EDP) as a teaching method to create the learning environment.