The contribution of change over time in parent and child characteristics to parents’ resolution of child's diagnosis was examined among 78 mothers and fathers of children with autism spectrum disorder. Children's characteristics (e.g., mental age and severity of symptoms), parental characteristics (e.g., attachment-related anxiety and stress level), and parents’ resolution of their child's diagnosis (resolved vs. unresolved) were examined at Time 1, and reassessed 3 years later at Time 2. Results indicated a deferential contribution of change in parent and child characteristics among mothers and fathers. An increase in child symptom severity and in maternal attachment-related anxiety, as well as longer durations of time since receiving the diagnosis, significantly predicted maternal resolved status at Time 2. Conversely, none of the changes in children's or paternal characteristics predicted paternal resolved status at Time 2. Results are discussed in relation to child and parental contributions to resolution, the differences in the adjustment and well-being of mothers and fathers of children with autism spectrum disorder, parental growth following receiving the diagnosis, and the need for intervention components specific to parental resolution and attachment-related anxiety.