The purpose of this study was to develop and psychometrically test the Social Capital Scale for families of children with special health care needs. Researchers have suggested a link between social capital and health, however, psychometrically tested measures of social capital are not described in the literature. The Social Capital Scale (SCS) demonstrated internal consistency, stability over time, and construct validity (as evaluated through factor analysis, correlation with existing measures, and hypothesis testing). Five subscales provide insight into family strengths and areas for improvement related to their investment in relationships that support health. Use of the SCS will contribute to the establishment of consensus and precision in communication about social capital's utility and measurement in the population of families of children with special health care needs.