Childhood cancer has a great impact on children and their environment. To minimize this, countries such as Canada and the USA have protocols in the field of social work, although these are scarce in Europe and especially in Spain. This paper aims to develop a pilot protocol in Aragon (Spain) for the practice of onco-pediatric social work in one of the hardest moments: the diagnosis. For its elaboration, a previous study was carried out in three phases, which provided data on the disease and its impact on the family and children and a methodological basis for the intervention from social work, all considering the participation of the agents involved as a fundamental element. Variables have been identified that influence the impact on the family support network and its quality of life at the time of diagnosis of childhood cancer. In addition, different indicators have been explored, based on the reality of these families. Finally, a pilot proposal for a comprehensive family intervention protocol in the diagnosis of childhood cancer has been elaborated. This work is intended to be a guide for intervention and delimitation of quality standards to be considered when dealing with the diagnosis of childhood cancer.