The explanatory sequential design was adopted for this study to explore the impact of student participation in the Individualized Education Plan (IEP) process on their perceived self-advocacy outside of the meeting. Quantitative data were collected through pre- and post-surveys and qualitative data were collected through student focus groups and teacher interviews. Participants included 111 students with disabilities in sixth, seventh, and eighth grades enrolled at a middle school in Georgia selected through purposeful sampling and seven teachers who were involved in the IEP process. Of the 111 students, 36 were selected to attend the focus group interviews. Paired t tests, ANCOVA, ANOVA and Welch’s F analyses were used to analyze the quantitative data; a deductive approach was used to analyze the qualitative data for this study. The findings showed IEP Participation had a positive impact on students’ perceptions of self-advocacy. Most of the students recognized the helpfulness of their IEP involvement, wanted to be more involved in their educational decisions, and noticed their own improvement on self-advocacy, especially in the pillars of “Knowledge of Self” and “Communication.” Although not many students specifically reported their improvements in the pillars of “Knowledge of Rights” and “Leadership,” teachers did notice increases in these two pillars. Special attention should be paid to students’ relationships with case managers and parental involvement because these would the possible factors influencing student participation in the IEP process. In addition, students from every middle school grade may improve self-advocacy perceptions from participating in the IEP process, although students in sixth grade may need additional support in the “Knowledge of Self” pillar due to their age and maturity. Furthermore, students from every eligibility category may improve self-advocacy perceptions from participating in the IEP process. After an explanation of self-advocacy, many of them are able to differentiate between the pillars of self-advocacy and state if they have improved or not in each pillar. Teachers and administrators may need to provide more supports for students with certain eligibilities (e.g., Autism, Speech-Language Impairment, and Intellectual Disability) who are struggling in some pillars.