Background Internationally, it has been recognised that parents need to advocate for their children with disabilities to receive services. However, many parents find advocacy difficult because of systemic and logistical barriers. As such, parents of children with disabilities may seek a special education advocate to help them understand their child's rights and secure services. Yet little research has been conducted about programmes to develop special education advocates. Methods In this study, we conducted a comparison study to determine the association of an advocacy programme (i.e. the Volunteer Advocacy Project) on a primary outcome (i.e. special education knowledge) and other outcomes (i.e. family–school partnership, empowerment and parent well‐being). Specifically, in 2017, 34 participants, all mothers of children with disabilities, were recruited from disability organisations in the USA. Seventeen mothers participated in the intervention group (i.e. the advocacy training), while 17 mothers participated in the wait list control group. The Volunteer Advocacy Project is a 36 hr advocacy training for individuals to gain instrumental and affective knowledge to advocate for their own children with disabilities and for other families. All participants completed a pre‐survey and post‐survey; only intervention group participants completed a 6‐month follow‐up survey. Results Compared with 17 wait list control group participants, the 17 intervention group participants demonstrated improvements in special education knowledge, P = 0.002, η2 = 0.32, and self‐mastery, P = 0.04, η2 = 0.15, and decreases in the quality of family–school partnerships, P = 0.002, η2 = 0.32. At the follow‐up survey, intervention group participants demonstrated increases in empowerment, P = 0.04, η2 = 0.29, and special education knowledge, P = 0.02, η2 = 0.38. Conclusions Implications for research including the need for a randomised controlled trial are discussed; also, practitioners need to evaluate advocacy training programmes regarding their effectiveness.