Ample research has investigated the relationship between team cohesion and on‐field behaviour, while the association between the first and off‐field prosocial behaviour has been almost overlooked. To fill this gap, we conducted a study in a sample of Italian Rugby Union athletes to examine whether: (a) team cohesion is associated with off‐field prosocial behaviour; and (b) the underlying mechanisms of this association. We focused on the two dimensions of team cohesion, that is social and task cohesion, and hypothesized that social cohesion should be associated with off‐field individual prosocial behaviour via empathy, while the association between task cohesion and off‐field individual prosocial behaviour should be mediated by on‐field fairplay team norms. In total, 497 amateur, sub‐elite, and elite Italian Rugby Union players (128 females) took part in this study by filling out an online survey. Results revealed that social cohesion was associated with greater empathy, which in turn was associated with greater expression of off‐field prosocial behaviour. Task cohesion was associated with both greater on‐field fairplay team norms and greater empathy, which in turn was linked to more off‐field prosocial behaviour. Results are discussed with respect to the role of team cohesion in favouring the expression of prosocial behaviour off‐field, thus underlying the role of sport in fostering moral behaviour (also) in everyday community life.