This study examines the relation between maternal warmth and the internalizing and externalizing problems of early adolescents, and the potential mediation of this relation by emotional insecurity. The hypotheses for the study derive from Cummings and Davies’ theory of emotional security. The current study extends the theory to security processes within the parent-adolescent relationship. A total of 203 early adolescents drawn from school samples in Spain participated in the study along with their mothers and their classroom teachers. The results supported the hypothesis. Emotional insecurity mediated the relationship between maternal warmth and adolescent internalizing and externalizing problems. Higher maternal warmth was linked to greater emotional security, which in turn was linked to fewer internalizing and externalizing problems. The findings extend the tenets of Emotional Security Theory and imply strategies for prevention and intervention.