We know little about custodial grandparents of children with autism spectrum disorder (ASD) who offer a vital social safety net. 117 custodial grandparents of children with ASD from 37 states completed an online survey with open-ended questions about their "greatest challenges and joys" as grandparent. Grounded theory analysis revealed four categories of experience (Issues with Adult Children, Caregiving Burden, Coping, & Wisdom) explained by 15 themes. Grandparents' stressors encompassed custody issues, ASD problem behaviors like tantrums and eloping, insufficient ASD services, financial burden, 24/7 caregiving demands, social isolation, and fears for the future. Grandparents' coping included celebrations of progress, unconditional love, faith, and a positive focus. Grandparents' wisdom included patience and insight. Recommendations to support these caregivers are provided.