The transition to kindergarten is regarded as a critical early childhood developmental milestone with important implications for later school outcomes. Little prior research has focused on predictors of socio-behavioral kindergarten outcomes using longitudinal research designs. Further, few studies have examined kindergarten transition using samples of children both with and without disabilities. The goal of the current study was to explore predictors of socio-behavioral kindergarten outcomes in children with and without developmental disabilities over time. Data collection involved parent, preschool teacher, and kindergarten teacher reports of child behavior and involvement in kindergarten transition practices across three time points during transition. Results of hierarchical linear regression analyses demonstrated that preschool child behavioral variables (i.e., adaptive and problem behavior) were stronger predictors of kindergarten outcomes relative to caregiver concerns and involvement in transition preparation. Best practices in kindergarten transition programming for children with and without disabilities are discussed. (author abstract)