Objective: To investigate levels of support and the concurrent and prospective effects of support on the psychological functioning of parents of children with cancer in a prospective longitudinal study. Methods: Parents' (n = 128) self-perceived level of psychological distress, quantity of support, and dissatisfaction with support were assessed, at diagnosis, at 6, and at 12 months. Results: Parents received most support at diagnosis. Self-perceived quantity decreased with time, but parents indicated they remained equally satisfied. Support significantly predicted concurrent and prospective distress of fathers, but not of mothers. Dissatisfaction with support and negative interactions were consistent risk factors for fathers. Mothers who adjusted well psychologically received more support and were less dissatisfied than mothers who remained clinically distressed. Nevertheless, no persisting effect of support was found. Conclusions: Findings illustrate that social support varies with the stress situation and with gender. Identification of vulnerable parents at diagnosis on the basis of their perception of received quantity of and dissatisfaction with support seems difficult. Intervention efforts aimed at mobilization of needed support may be efficacious.