The purpose of this research was to predict social problem-solving skills in two dimensions (functional and dysfunctional), based on birth order and attachment styles in university students. For the study, 234 students were randomly selected at Azad University in the Science & Research Branch, who completed two questionnaires: Hazen & Shaver’s Attachment Styles Inventory (AAI) and D’Zurilla et al.’s Social Problem Solving Skills Inventory-Revised (SPSI_R). Data were analyzed with multiple regression and MANOVA tests. The results revealed that avoidant and anxious attachment styles had significant and positive relationship with dysfunctional social problem solving, and had significant and negative relationship with functional social problem solving skills; and birth order significantly predicted dysfunctional social problem solving. Also, a comparison of the first and last children showed that a significant difference existed between the mean of first and last children in avoidant attachment style (first children were higher than that of last children). But there is no significant difference between first and last children in the dimensions of social problem-solving skills.