Advocacy has long been heralded as a way to create change for individuals with intellectual and developmental disabilities (IDD) and their families. However, without an established measure, it is difficult to accurately characterize advocacy activities. Drawing from extant research, the Advocacy Activities Scale was developed to assess three domains of parent advocacy: advocacy for one's own children, advocacy for other families, and advocacy for systemic change. Factor analyses were conducted using data from two projects reflecting 382 parents of individuals with IDD from seven states and the District of Columbia. The scale confirmed the three moderately correlated domains of parent advocacy and demonstrated that the scale has high: reliability, validity, test-retest reliability, and moderate correlations with related measures.