This study examined the relations between preschool children's attachment security, temperament, and peer acceptance. Ninety-eight preschool children and their mothers were recruited through childcare centers in the southeast. Mothers and their children participated in two two-hour home observations. Attachment security was assessed using the Waters Attachment Behavior Q-set (AQS) completed by observers, and mothers reported on their children's temperament. Standard picture-sociometric nominations and paired-comparisons were used to measure children's peer acceptance. Results revealed significant associations between security and temperament. In addition, both attachment and temperament made significant and unique contributions to peer acceptance whereas temperament was found to be a stronger predictor of children's peer rejection. These findings underscore the dynamic interplay of inter- and intrapersonal factors that influence preschool children's peer relations. Implications of the findings for theory building and future research are discussed.