Status hierarchies often emerge in small collective task groups. In these groups, clearly defined hierarchies facilitate and stabilize structured cooperative interactions among group members, supporting their evolutionary function in the real world. What the existing research in this field has failed to consider, however, is that cooperation matters in these hierarchies with clear status inequality, as well as in other more realistic, multiple-leader groups with less clear hierarchies. Multi-leadership is ubiquitous but, by definition, flattens status inequality and may, in turn, jeopardize its capacity to sustain cooperation. Leveraging the relationship between multi-leadership and cooperation, our evolutionary game model reveals that hierarchies, in general, promote cooperation in groups with multiple leaders, but these hierarchies only do that up to a point, after which multi-leadership backfires. Accordingly, the model provides not only a theoretical account for how multi-leadership coexists with cooperation but also the conditions under which the coexistence would break.