In this chapter, we consider the development of emotion regulation (ER) and its role in child adaptation broadly construed, with the goals of (1) elucidating some of the complex mechanisms and pathways that are operating in development; (2) citing challenges and controversies that have emerged through the study of ER; and (3) advocating for an integrated biopsychosocial approach to the study of ER in the next generation of theory and research in this area. We organize the chapter in five sections: (1) definitional and theoretical considerations; (2) developmental and contextual issues; (3) empirical approaches and challenges; (4) relations to child outcomes (including psychopathology, social competence, and academic achievement); and finally (5) implications and challenges for future research. Our overarching aim is to go beyond a summary of research findings to highlight the many conceptual and empirical issues that ought to be considered in studies examining the relation between ER and child outcomes related to developmental psychopathology.