Parents, but also entire families of children with developmental disabilities, specifically children with Down syndrome, are a rare topic of research, especially in Croatia. It is important to research this topic in order to improve the functioning of the family, organize interventions and therapies for the child, but also for the parents. The aim of this study was to examine the differences in stress, satisfaction of needs and mental health of parents with regard to the age of the child with Down syndrome, and to examine to what extent stress and needs explain the mental health of parents. Eighty three parents of children with Down syndrome (70 females and 13 males) participated in this study, with age range from 31 to 65 years, and they were contacted through associations for Down syndrome throughout the Republic of Croatia. The research was conducted using an online questionnaire, and the hypotheses were only partially confirmed. Significant negative correlations were found between the child's age and some sources of parental stress (demandigness, child's health, incompetence, relationship with the partner, limitations of the parental role, demands of other roles) and a negative correlation was obtained between child's age and parental depression. Parents od younger children report greater intensity of stress in the mentiond aspects and greater expression of depression symptoms. Differences in the expression of different sources of stress, needs and mental health with regard to the age of child were obtained only for the stressor related to the characteristics of parents and social support, while no differences were found for needs, anxiety and depression. Also, the child's age and total stress significantly contribute to the explanation of parental depression, while only the total stress significantly contributes to the explanations of parental anxiety. The needs directed at the child and the parents did not prove to be significant predictors in the explanation of the parental mental health. This research allows us to detect some important sources of stress for parents of children with DS of different ages and how they reflect on the psychological functioning of parents.