This study examines the extent to which teacher–student relationships, peer relationships, and family involvement can be used to predict a sense of school belonging among adolescents, according to gender. The sample of the study consists of 815 students enrolled in nine state primary schools in the central districts of Mersin, Turkey. The data was gathered with “Sense of School Belonging,” “Teacher–Student Relationships,” “Peer Relationships,” and “Family Involvement” sub-scales, after adapting these into Turkish, and then analyzed through a stepwise regression analysis statistical method. The results of the analyses for the total sample revealed that teacher–student relationships, peer relationships, family involvement at home, and family involvement at school are the respective significant predictors of a sense of school belonging among adolescents. The results also indicated that both teacher–student relationships and the peer relationships play a significant role in the ability to predict a sense of school belonging for both genders. However, it was also found that family involvement at school has a significant predictive role in a sense of school belonging among boys, whereas family involvement at home has a significant predictive role in a sense of school belonging among girls.