The bystander effect, the phenomenon that the (real or imagined) presence of others inhibits helping, has often been ascribed to bystanders’ apathy. In the present research, we demonstrate that the occurrence of the bystander effect has rational roots. Three studies reveal that the presence of other bystanders does not inhibit helping when effective helping requires more than one help‐giver. Mediation analyses showed that the bystander effect did not occur when many responses were needed because bystanders did not shift responsibility to others when in the presence of other bystanders. These findings suggest that the rational considerations underlying the bystander effect can mitigate the effects of the presence of other bystanders on helping behaviour when more than one help‐giver is needed.