Children's experiences within their peer group and family have occupied a central position of importance in research within developmental, social, and clinical psychology. The purpose of the current investigation was to integrate the literatures on the development of the self (i.e., the actual, ideal, and undesired selves) and significant interpersonal relationships, particularly best friendships and parent-child relations, in order to examine the developmental significance of such close relationships on the construction of the adolescent self-portrait. An additional focus was to examine how the self-portrait and these significant relationships relate to subsequent psychological adjustment, specifically depression and self-worth. Finally, exploratory consideration was given to gender differences and how factors regarding gender differences relate to subsequent emotional adjustment. Self-report questionnaires were used to examine the linkages among the self-portrait, significant interpersonal relationships, and psychological adjustment in a sample of 118 early adolescent participants and their mothers. Findings revealed that self-discrepancies, from one's own standpoint and the standpoint of a significant other, were associated with psychological adjustment. Relational quality was found to have a moderating effect with regard to the actual-own and undesired-own self-discrepancies on depression, but not on self-worth. In addition, parents had more influence on their children's ideal self and the undesired self than their best friends. Adolescent relationships with mothers, fathers, and best friends characterized by higher relationship security were found to have more influence on particular domains of the adolescent self-portrait than relationships characterized by low relationship security. Adolescents who reported better relationship security in their significant relationships reported more positive psychological adjustment. Finally, the associations between relational security and psychological adjustment generally were not moderated by the maternal assessment of relational security. By integrating the theories and research pertaining to self-development, friendship, and parent-child relations, the current investigation extends prior research by considering the contributions that formative relationships make on adolescent self-related processes, and ultimately the dual impact that the formative relationships and the self have on psychological and socioemotional adjustment. In general, the findings highlight the importance of significant interpersonal relationships on the development of the adolescent self-portrait, and ultimately psychological adjustment.