A process evaluation was conducted to determine the effectiveness, usability, and barriers and facilitators related to the Better OutcOmes amp; Successful Transitions for Autism (BOOST-A (TM)), an online transition planning program. Adolescents on the autism spectrum (n = 33) and their parents (n = 39) provided feedback via an online questionnaire. Of these, 13 participants were interviewed to gain in-depth information about their experiences. Data were analyzed using descriptive statistics and thematic analysis. Four themes were identified: (i) taking action to overcome inertia, (ii) new insights that led to clear plans for the future, (iii) adolescent empowerment through strengths focus, and (iv) having a champion to guide the way. The process evaluation revealed why BOOST-A (TM) was beneficial to some participants more than others. Trial registration #ACTRN12615000119594.