Emotional security theory was introduced over two decades ago to explain how and why children exposed to interparental and family conflict are at greater risk for developing psychopathology. Using developmental psychopathology as an evaluative lens, this chapter provides a review of the progress, challenges, and future directions in testing EST. After characterizing the distinctive properties of the goal system of emotional security in relation to developmental constructs outlined in other approaches, we review empirical evidence supporting the hypothesis that emotional insecurity is a unique and robust mediator of multiple pathways involving family adversity and children's adjustment problems. Next, the chapter addresses the family, contextual, developmental sources underlying the multiplicity of pathways among family discord, emotional insecurity, and children's psychological functioning. Throughout the chapter, we distinguish between two formulations of EST to adequately characterize the significant developments in the history of the theory. Finally, we conclude by outlining scientific and clinical growing points for EST.