In the present study, the effects of structural quality of day care centers on the social competence of children were investigated. 101 6-year-old children were chosen from the 13 different day care centers. Their social competencies were evaluated by teachers' ratings and peer nominations. The results indicated that after considering family education level and length of day care attendance, with respect to teacher ratings, negative interactions with peers were significantly predicted by group size and square footage per child. With respect to peer nominations, unoccupied behaviors of children were significantly predicted by length of last day care experience and also solitary behavior of children were significantly predicted by the total frequency of picture book reading, educational and other activities. The implications and limitations of this study are also discussed.