The effects of person‐ and process‐focused feedback, parental lay theories, and prosocial self‐concept on children's prosocial behavior were investigated with 143 9‐ and 10‐year‐old children who participated in a single session. Parents reported entity (person‐focused) and incremental (process‐focused) beliefs related to prosocial behavior. Children completed measures of prosocial self‐concept, then participated in a virtual online chat with child actors who asked for help with service projects. After completing the chat, children could assist with the service projects. In the first cohort, children were randomly assigned to receive person‐focused, process‐focused, or control feedback about sympathy. In the second cohort, with newly recruited families, children received no feedback. When given process‐focused feedback, children spent less time helping and worked on fewer service projects. When given no feedback, children spent less time helping when parents held incremental (process‐focused) beliefs. Children with higher prosocial self‐concept who received no feedback worked on more service projects.