One striking characteristic of human social interactions is unconscious mimicry; people have a tendency to take over each other's posture, mannerisms and behaviours without awareness. Our goal is to make the case that unconscious mimicry plays an important role in human social interaction and to show that mimicry is closely related to and moderated by our connectedness to others. First we will position human unconscious mimicry in relation to types of imitation used in cognitive psychology and cognitive neuroscience. Then we will provide support for social moderation of mimicry. Characteristics of both the mimicker and the mimickee influence the degree of mimicry in a social interaction. Next, we turn to the positive social consequences of this unconscious mimicry and we will present data showing how being imitated makes people more assimilative in general. In the final section, we discuss what these findings imply for theorizing on the mechanisms of imitation and point out several issues that need to be resolved before a start can be made to integrate this field in the broader context of research on imitation.