Commuting with peer companions during school travels, children can share their school life, personal feelings and even secrets with others, and this may strengthen their peer relationships in schools. This study empirically explored the relationships between school travel and the peer relationships of children. The sample data were collected using a social cognitive map survey of sixth grade students at an elementary school located in a major city in northern Taiwan. The peer relationships were comprehensively measured by social network indicators and were analyzed using regression methods with the explanatory variables of travel companions, as well as physical, mental, external performance and family attributes. Empirical results indicate that school travel companions affect the peer relationships of children. Specifically, more time spent accompanying peers during school travels elevated children’s peer relationships while being escorted by adults during travel to school declined peer relationships. This study not only provides new knowledge of the determinants of the peer relationships of children but also significant fresh policy directions in relation to school transport in developing the social capability of children.