Students with intellectual and developmental disabilities (IDD) who attend inclusive postsecondary education (IPSE) programs gain many new and beneficial skills, including independent living, social, and employability skills. Another skill set that may be strengthened by attending an IPSE program is self-determination. There is limited research available identifying the impact of IPSE programs on self-determination growth. We addressed this gap by using a longitudinal study designed to examine the changes in self-determination levels of students with IDD across 3 years in an IPSE program. Data collected from 23 students with IDD at 4 points of time within 3 years showed that there was an increasing trend in students' self-determination levels at the end of each year. The difference was highly significant between the baseline and the end of the third year. This suggests that IPSE programs can play a critical role in the improvement of the self-determination levels in students with IDD. Implications and future research are discussed.