In this research, the relationship of attachment styles and social self-esteem were examined. The main goal of the current research was to study the type of relationship of secure attachment style, avoidant attachment style, anxious/ambivalent attachment style with social self-esteem. Number of 84 post graduate and doctoral students in Ferdowsi university of Mashhad (52 male and 32 female) participated in this research. Subjects are asked to complete Adult Attachment Questionnaire (AAQ), Revised Adult Attachment scale (RAAS), and social self-esteem inventory. To analyze research data, statistical methods such as mean, standard deviation, correlation coefficients and regression analysis were used. Research conclusions showed that secure attachment style, avoidant attachment style. anxious/ambivalent attachment style can significantly explain variation of social self esteem variable,(P<0.05, P<0.01). That is increasing in secure attachment style lead to increased social self esteem and increasing in avoidant attachment style and anxious/ambivalent attachment style lead to decreased social self-esteem. Attachment styles affect social self-esteem through affecting the quality of social relationships (either positive or negative) and lead to increased or decreased social self-steam.