Empathy is commonly considered a driver of prosociality in child ontogeny, but causal assumptions regarding this effect mostly rely on correlational research designs. Here, 96 urban German children (5–8 years; 48 girls; predominantly White; from mid-to-high socioeconomic backgrounds) participated in an empathy intervention or a control condition before prosocial behaviors (polite lie-telling: rating the drawing as good ; prosocial encouragement: utterances interpreted as cheering up the artist) were assessed in an art-rating task. Contrasting children’s empathy at baseline with their empathy after the intervention indicated promoted empathy compared to the control group. Despite the intervention’s effect on children’s empathy, there were no simultaneous changes in prosocial behaviors. At the same time, children’s empathy at baseline was associated with their prosocial encouragement. These results indicate conceptual associations between children’s empathy and prosociality. However, they do not support strict causal claims regarding this association in middle childhood. Further applications of the novel short-time intervention to address causal effects of empathy on prosociality and other developmental outcomes are discussed.