This research aimed to develop and evaluate an online problem-based learning (PBL) model to enhance undergraduates' self-regulated learning (SRL). The Research and Development method was used in two phases: the first was to develop and validate the model. It began with a literature review to identify core features of effective PBL and SRL within an online environment, then set a concept framework and create the model manually. Seven experts were reviewed following the model, and it was piloted for further optimization. Second, the model will be implemented and evaluated with a sample of 52 students at Thailand National Sports University, Chumphon Campus. The main instruments used were the developed model, the model quality questionnaire, SRL assessments (pre- and post-), and after-action review forms. The results showed that (1) a developed model consisting of four sections: orientation of the model, the model of instruction, application, and student outcomes. Six core components: authentic problems, online collaborative learning, self-regulated learning, instructional scaffolding, online learning resources, and authentic assessments, which are organized through three main processes: preparation, implementation of SRL strategies, and summative assessment, and all activities using an iterative learning three stages: meeting the problem and planning, doing and checking, and presenting the result and reflecting. Experts agreed on the quality of this model, which was excellent. (M= 4.61, SD=0.52). (2) Average SRL score was significantly higher after learning with this model compared to prior us (p<0.01, large effect size; d=1.03). The findings of this study support the developed model that can improve the students' SRL effectiveness. Overall, the students agreed that an instructor plays a critical role in developing their SRL and problem-solving skills. The students demonstrated more self-assurance and were apt to use this method to learn other subjects.