Sports are social, and the sociability of sports (e.g. individual experiences, group cohesion or generalised social trust) and its consequences (e.g. enjoyment, inclusion, or social capital) depends on the social networks in sports teams. In this study we investigate various types of social networks in sports-strong and weak-for boys and girls. We look at the number of social relations in each team (average degree), how centralised and hierarchical teams are, and how each team clusters and consists of subgroups. We hypothesise that: (i) Boys' and girls' teams differ in number of social relations, (ii) Boys' social networks are more hierarchical than girls' networks, and (iii) Girls' teams are more clustered than boys' teams. Network data from 387 adolescent athletes on 30 sports teams in football, handball, crosscountry skiing and biathlon were collected with an electronic survey-questionnaire. The results reveal large differences in network structures between teams. We find that the total number of social relations is higher in girls' teams, that there are small gender differences with respect to networks' hierarchies, and that girls' networks cluster more than boys' networks.