Being a parent of a child diagnosed with cancer poses an enormous stressor. Indeed, several parents have difficulties adjusting to such a situation and react with symptoms of traumatic stress, depression, and reduced quality of life. However, there is little conceptual work on behavioral mechanisms that contribute to suboptimal adaptation in these parents. The authors present a conceptualization in which experiential avoidance and rumination are suggested to contribute to increased levels of traumatic stress and suboptimal adaption. Based on this conceptualization, a recently developed intervention for parents of children with cancer, in the form of guided self-help, is presented. Finally, the authors present a successful case study as an example of the application of this intervention. Clinical implications and suggestions for future research are discussed.