We sought to identify, examine, and summarize empirical literature focused on early childhood behavior interventions examined using a single case research designs (SCD) and published between 2001 and 2018. Using systematic procedures, 28 studies that met established inclusion criteria were identified, reviewed, and compared with respect to general and social validity assessment characteristics of SCD studies on behavior interventions for young children with problem behavior. The findings of the current review suggest: (a) promoting implementation fidelity through implementation support to improve social validity outcomes, (b) providing guidelines for timing and frequency of social validity assessment, and (c) development of social validity assessment tools designed to assess each of the social validity dimensions (i.e., goals, procedures, and outcomes).