Self-determination, as a vital topic for individuals with disabilities, has received a narrow investigation in Saudi Arabia and the Middle Eastern communities. Therefore, it is imperative to examine evidence-based practices to furnish insight into the efficacy of self-determination models not only through theoretical research methods but also via practical and empirical methods. Therefore, this study aims to examine the impact of the Self-Determined Learning Model of Instruction (SDLMI) on the abilities and skills associated with self-determination among high school Saudi female students with Intellectual and Developmental Disabilities (IDDs) aged 16-21. The Self-Determined Learning Model of Instruction (SDLMI) is one of the evidence-based models developed to promote student self-determination by guiding educators to enable students to set goals, take action plans to attain those goals, and self-evaluate their progress. SDLMI is grounded in Causal Agency Theory, a theoretical framework for apprehending and conceptualizing the self-determination of people with and without disabilities. A quasi-experimental design was used in this study to explore the effect of the SDLMI on four components of self-determination (autonomy, self-regulation, psychological empowerment, and self-realization), assessed by the Arabic version of Arc's SDS that has been previously standardized and validated to suit the Saudi culture. The participants were 76 students; 39 were assigned to the treatment group (TG) and 37 to the Control group (CG). The fidelity of the implementation was measured using several tools. The results indicated that SDLMI had significantly increased the total scores of self-determination and its four components for the treatment group. Recommendations for future research, educators, parents, and policymakers, and related implications for advancing up efforts to promote self-determination within Saudi contexts, are provided. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]