Youth with autism spectrum disorder (ASD) face challenges accessing needed services as they transition to adulthood. Correlates of service access identified in the literature--such as family resources, race/ethnicity, or youth functioning--can be difficult to change and may not be feasible targets for intervention. This study focused on a potential contributor to service access that is malleable: parental advocacy. Specifically, we examined the association between parental advocacy activities and number of services among transition-aged youth with ASD, after accounting for indicators of youth functioning and family demographic variables (high school exit, co-occurring intellectual disability, social impairments, adaptive behaviors, race/ethnicity, state of residence, family income, and parental depression). Participants included 185 families of youth with ASD who are part of an ongoing randomized controlled trial. Data were collected at baseline (prior to intervention) via parental questionnaire and structured interview. Using hierarchical regression analyses, we found that parental advocacy activities were significantly and strongly associated with service receipt after controlling for youth functioning and family demographic factors. Youth whose parents are less involved in advocacy activities might be at-risk for service disparities. To close the gaps for service disparities, future interventions may target parental advocacy skills.