Individuals have a drive towards maximising action efficiency – given a choice of two actions to achieve the same goal, they will choose the action that incurs fewest costs. In joint actions, actors prioritise joint efficiency or co-efficiency, maximising the utility of the joint action even if this comes at a cost to themselves. However, when acting jointly it may also be important to consider factors other than efficiency, such as fairness. We investigate whether the reputational motivation to be seen as fair will interfere with participants’ drive to maximise co-efficiency. We present the results of two experiments where participants complete the first part of a two-step joint action with a partner and have to decide between a fair action that requires equal contribution from both agents, and an unfair action that disadvantages either themselves or their partner. Participants consistently and reliably act in a way that maximises co-efficiency regardless of fairness or the costs that they incur individually, but they also take longer to perform actions that are unfair to their partner (rather than themselves). This suggests that although participants are sensitive to (un)fairness in task distribution they do not let this affect their decisions.