Longitudinal research into the development of prosociality during childhood contributes to our understanding of individual differences in social and emotional outcomes. There is a dearth of literature on the development of prosociality in children with Developmental Language Disorder (DLD). Data from the UK based Millennium Cohort Study was used to investigate prosociality from age 5 to 11 years in 738 children at risk of Developmental Language Disorder (r-DLD) and 12,972 children in a general population (GP) comparison group. Multilevel mixed effects regression models were run to investigate the mean change in prosociality and latent class growth analysis was used to identify heterogeneous groups of children who shared similar patterns of development. Overall, children at risk of DLD were less prosocial at age 5 and, although they did become more prosocial by the age of 11, they did not reach the same levels of prosociality as those in the GP group. Subsequent sub group analysis revealed four distinct developmental trajectories: stable high (19 %), stable slightly low (36 %), decreasing to slightly low (5 %), and increasing to high (40 %). Children at risk of DLD were less likely than those in the GP group to be in the stable high class and more likely to be in the stable slightly low class. For children at risk of DLD, being prosocial was protective against concurrent social and emotional difficulties. But being prosocial in early childhood was not protective against later social and emotional difficulties nor did the absence of prosociality in early childhood make social and emotional difficulties in middle childhood inevitable. Rather, the presence of prosociality in middle childhood was the key protective factor, regardless of prosociality in early childhood. Prosociality is not a key area of concern for children at risk of DLD. Instead, it is an area of relative strength, which can be nurtured to mitigate social and emotional difficulties in children at risk of DLD, particularly in middle childhood.