Posttraumatic growth theory posits that when life circumstances are perceived as stressful, secondary appraisal processes can be recruited in ways to facilitate both coping efforts and personal growth. Using a mixed-methods approach, we found mothers’ most challenging experiences involved child behavior (e.g. aggression, communication, and social issues) and psychosocial impacts (e.g. lack of social support, perceived judgment of others, perceived loss, and personal distress). Descriptions of most rewarding experiences reflect posttraumatic growth frameworks including constructive perceptions about themselves, life, and their relationships as well as evidence for what Maercker and Zoellner call illusory types of posttraumatic growth. Quantitative data were subjected to a hierarchical regression analysis for self-reported posttraumatic growth and included mothers’ demographics, child functioning, and psychosocial measures. As predicted, posttraumatic growth was positively associated with social support from mothers’ most important network member and quiet ego characteristics, a type of eudaimonic motivation. Contrary to expectation, neither autism spectrum disorder–related rumination nor time since diagnosis (or their interaction) was associated with posttraumatic growth. Discussion focuses on the practical implications of our findings that posttraumatic growth-related coping includes both constructive and illusory forms and the importance of social support and eudaimonic motivation in facilitating positive forms of secondary coping.