Choosing adequate partners is essential for cooperation, but how children calibrate their partner choice to specific social challenges is unknown. In two experiments, 4- to 7-year-olds (N = 189, 49% girls, mostly White, data collection: 03.2021-09.2022) were presented with partners in possession of different positive qualities. Children then recruited partners for hypothetical tasks that differed with respect to the quality necessary for success. Children and the selected partner either worked together toward a common goal or competed against each other. From age 5, children selectively chose individuals in possession of task-relevant qualities as cooperative partners while avoiding them as competitors. Younger children chose partners indiscriminately. Children thus learn to strategically adjust their partner choice depending on context-specific task demands and different social goals.