Background: ASD in a child affects parental mental health, with elevated levels of stress, anxiety and depression reported in parents. Method: In this study, we examined mothers' and fathers' stress, anxiety and depression, as well as their coping strategies in a sample of 103 children and adolescents enrolled in the ELENA cohort study in France at diagnosis and three years after diagnosis. Results: Results showed that mothers had higher levels of stress and anxiety / depression than fathers and used more social support coping strategies at diagnosis, which might be explained by increased levels of parental involvement. Mothers’ stress level significantly decreased during the three years following ASD diagnosis but no such decrease was observed in fathers’ stress level. A significant decrease in anxiety and depression was observed for both parents, suggesting that parental distress is particularly elevated during the critical diagnosis period. Results finally yielded a significant decrease in emotion-focused coping strategy in mothers over the three-year period, an ineffective strategy that takes places at the time of diagnosis but then decreases during the period following ASD diagnosis, in relation to the acceptance process. Conclusions: Implications in terms of addressing the unmet mental health needs of parents and their coping strategies are discussed.