This research aimed to evaluate the effectiveness of including an instructional design training workshop for teachers in the summer training program in their teaching performances. The study utilized mixed methods, such as focus groups, participant observation, and data analysis, to measure the program's impact on teachers' competency in achieving learning outcomes and improving the educational process. Sixty teachers participated in the study, attending the three-day workshop for five hours daily, which was presented multiple times during the summer of 2019. The participants' feedback was collected during and after completing the course and after an entire semester of teaching to assess the practical application of the workshop's teachings. The results showed that in the instructional design training workshop, statistically significant variances were observed in all stages of ADDIE postevaluation. T-values ranged from -9.78 to -11.34, with p-values less than 0.01. The overall mean score for all phases of ADDIE was -9.87 at p<0.01, and it significantly enhanced the teachers' skills and competencies and fostered their interest in further professional development. The study recommends that teacher training programs focus on enhancing instructional design skills and ongoing professional development to inform educators about the latest teaching practices and techniques.