Currently, information about the psychometric properties of the Social Support Networks Scale (SSNS) for family caregivers of children with cancer is not yet available; therefore, there is no empirical evidence of its validity and reliability to support its use in this population. The aim of this study is to determine a factorial model of the SSNS, estimate its internal consistency reliability, describe its distribution, and check its concurrent validity. A convenience sample of 633 family caregivers of children with cancer hospitalized in a National Institute of Health in Mexico City was collected. The SSNS, a sociodemographic variables questionnaire, and three instruments that evaluated family functioning, quality of life, and resilience were applied. The five-factor model had a poor data fit and lacked discriminant validity. The sample was divided. In a subsample of 316 participants, exploratory factor analysis suggested a four-factor model. When testing the four-factor model through confirmatory factor analysis, religious support was independent of family support, friend support, and lack of support. In the other subsample of 317 participants, the one-factor model for religious support had a good fit, and the correlated three-factor model, with the remaining factors, showed an acceptable fit. Reliability ranged from acceptable (Guttman’s λ2 = 0.72) to good (λ2 = 0.88). Socio-family support and its three factors were correlated with family functioning, resilience, and quality of life. Religious support was correlated with four factors of resilience and quality of life. A scale of socio-family support with three factors and an independent scale for religious support are defined from the SSNS, and they showed internal consistency and construct validity.