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Groups of people often find it challenging to coordinate on a single choice or option. Even when coordination is achieved, it may be inefficient because better outcomes were possible. Numerous researchers attempted to address this coordination problem with various manipulations ranging in complexity and generalizability, but results were mixed. Here, we use a more parsimonious and generalizable method – counterfactuals – to nudge (i.e. indirectly guide and allow for free choice) individuals towards choosing options that are more likely to result in efficient coordination. We used a modified version of an existing coordination game, the minimum effort game (MEG), where we added actual effort (i.e. solving an arithmetic problem) and counterfactuals (i.e. statements highlighting the hypothetical outcomes had they or other players chosen differently). Based on previous literature and promising results from a pilot experiment using bidirectional counterfactuals (i.e. both upward and downward), we designed and preregistered a follow-up experiment to directly assess the effectiveness of counterfactuals. We replicated the pilot study with a bidirectional counterfactual condition, then added an upward, downward, and control (no counterfactuals) condition. We found weak evidence for counterfactual nudging and clear evidence that players can effectively nudge the group towards higher efficiency.