This research used the Research and Development (R&D) methodology, which has research steps in the form of R1D1...R2D2...RiDi to get an educational innovation called "Online Self-Training Program to Development for Teacher's 21st-Century Skills Enhancement into Effective Practices" that is effective. It is an educational innovation with certified research results that can be used and disseminated to benefit development in schools that are the target population on a large scale. The online self--training program consisted of 2 projects: (1) Development Project for Teachers' Learning with six self-training modules used to develop teachers; and (2) The Project for Teachers to Bring Learning Outcomes into Practice with Students with one self-training module to be used as a guideline for teachers. The results of the experimental research in the first project revealed that among the experimental group of 17 teachers, the learning outcomes had met the standard of the 90/90 criteria. Moreover, the average test scores after the experiment had been significantly higher than before the experiment, according to statistical analysis. In the experimental research of the second project, it was found that among the 510 students involved in the experiment, the average scores from the assessment of perception towards teachers' practices had been significantly higher after the experiment compared to before the experiment. It was found that the research results aligned with the pre-determined research hypotheses, indicating the effectiveness of educational innovations resulting from the research. These findings can be utilized to enhance and cultivate 21st-century skills for teachers in the targeted schools, demonstrating the potential for future research dissemination and application.