Prosocial behaviours, actions that benefit others, are crucial for social relationships and healthy life. These behaviours could be framed as a cost-benefit decision-making, where the cost is incurred by the agent, but the benefit is received by someone else. Here, I discuss the advantages of framing prosocial decisions under a cost-benefit framework. This framework could help us to understand prosocial variability between people, including links to psychiatric disorders, and variability between contexts, including global challenges such as climate change and infectious diseases. It could also provide mechanistic underpinnings for these behaviours, and identify factors that facilitate them. Thus, despite having limitations and challenges, this framework is useful to examine and understand prosocial motivation.