We investigated if group music training in childhood is associated with prosocial skills. Children in 3rd or 4th grade who attended 10 months of music lessons taught in groups were compared to a control group of children matched for socio-economic status. All children were administered tests of prosocial skills near the beginning and end of the 10-month period. Compared to the control group, children in the music group had larger increases in sympathy and prosocial behavior, but this effect was limited to children who had poor prosocial skills before the lessons began. The effect was evident even when the lessons were compulsory, which minimized the role of self-selection. The results suggest that group music training facilitates the development of prosocial skills.