Prosocial behaviors are essential for social bonding and cohesion, but the mechanisms that underpin these behaviors are still poorly understood. Using computational modeling and neuroimaging, we show that people can learn to benefit others and that this learning is underpinned by reinforcement learning signals in the subgenual anterior cingulate cortex (sgACC). However, there is substantial individual variability in people’s ability for prosocial learning. More empathic people learn faster and have more selective responses in the sgACC when benefitting others. Our results thus reveal a computational mechanism driving prosocial learning in humans and why empathy and prosocial behavior may be linked. This framework could help to explain reduced empathy and prosocial behavior in people with disorders of social cognition.