Idrottslyftet (“a boost for sport”) is a Swedish government-financed sports initiative aiming to activate more young people through sports. One way to achieve this aim is through cooperation between school and sport clubs, whereby a sport coach runs sport activities during the school day. The goal of this article is to analyze how gender relations are shaped, reproduced, or challenged through practices within a co-ed soccer project. An ethnographic field study was conducted in two elementary school classes. The result draws on participant observations of interactions between coach and children, and between the children themselves, and is analyzed through critical discourse analysis and theories of gender relations. A focal point of the analysis is how gender relations are shaped by the use of language (including body language). The result suggests that children are active in shaping and challenging boundaries between girls and boys; however, the structure of the football lesson as well as the coach’s actions and non-actions are also important in shaping gender relations. To enable equality in co-ed sport projects, coaches should be aware of their actions and how they may affect the children that they are teaching, and should also attend to the children’s own gender boundary setting.