Humans constantly coordinate their actions with those of others, ranging from a handshake to the building of a house. What are the processes enabling individuals to perform such joint actions? The present work targets this question by investigating to what extent individuals integrate others’ task constraints into their own actions when acting together. The first study explored whether individuals represent and adapt to a co-actor’s movement constraint to achieve temporal coordination even if this implies compromising the efficiency of their own movements. The results showed that unconstrained individuals represented the obstacle obstructing their co-actor’s movement path such that they moved as if an obstacle was obstructing their own path as well. A second study investigated whether co-actors represent the order of actions within each other’s action sequence. Co-actors experienced interference when performing the same actions in a different order compared to the same order, indicating that they represented the order of each other’s actions, although this was not necessary for joint task performance. A third study asked whether and how co-actors create novel communication systems to solve a coordination problem. Depending on situational factors, informed actors communicated by engaging in novel forms of sensorimotor communication or of symbolic communication. In sum, these studies show that individuals possess a distinct tendency to take others’ task constraints into account when faced with the challenges of real-time action coordination. Specifically, individuals represent the difficulty, the goal states, and the temporal structure of others’ actions, as well as the task knowledge others possess, and they integrate these constraints into their own actions even if this compromises individual efficiency. If overcoming another’s task constraint requires an active transfer of information, individuals flexibly create novel communication systems. Taken together, the work presented in this thesis contributes to a better understanding of the processes underlying joint action and it provides further indication of the human predisposition to act with others in mind.