The discovery of mirror neurons has given rise to a number of interpretations of their functions together with speculations on their potential role in the evolution of specifically human capacities. Thus, mirror neurons have been thought to ground many aspects of human social cognition, including the capacity to engage in cooperative collective actions and to understand them. We propose an evaluation of this latter claim. On the one hand, we will argue that mirror neurons do not by themselves provide a sufficient basis for the forms of agentive understanding and shared intentionality involved in cooperative collective actions. On the other hand, we will also argue that mirror neurons can nevertheless play an important role in an account of the production and understanding of joint action, insofar as they provide the basic constituents of implicit agent-neutral representations and are useful elements in a process of online mutual adjustment of participants' actions.