Research Findings: A successful transition from preschool to elementary school requires a high level of behavioral adaptation. The aim of our study was to analyze child-related factors in preschool that facilitate a positive behavioral adaptation in the transitional period to elementary school. A cluster analysis was conducted with the data from 406 preschoolers, in order to identify profiles based on self-regulation skills, social-emotional competences, and externalizing behavior problems. Using structural equation modeling, we then tested a regression model to examine which preschool profile adequately manages to adapt their behavior for elementary school. The profile clustering showed that behavior problems occurred when self-regulation skills were low, despite existing (moderate) social-emotional competences. Moreover, low levels of self-regulation skills in preschool predicted difficulties in behavioral adaptation at school, especially concerning hyperactivity, even when children possessed moderate social-emotional competences. Practice or Policy: Most notably, the results reinforce the relevance of promoting early self-regulation skills to support children in their behavioral adaptation process during the transitional period from preschool to elementary school.