Most child studies on emotion perception used faces and speech as emotion stimuli, but little is known about children's perception of emotions conveyed by body movements, that is, emotional body language (EBL). This study aimed to investigate whether processing advantages for positive emotions in children and negative emotions in adults found in studies on emotional face and term perception also occur in EBL perception. We also aimed to uncover which specific movement features of EBL contribute to emotion perception from interactive dyads compared with noninteractive monads in children and adults. We asked 5-year-old children and adults to categorize happy and angry point-light displays (PLDs), presented as pairs (dyads) and single actors (monads), in a button-press task. By applying representational similarity analyses, we determined intra- and interpersonal movement features of the PLDs and their relation to the participants' emotional categorizations. Results showed significantly higher recognition of happy PLDs in 5-year-olds and of angry PLDs in adults in monads but not in dyads. In both age groups, emotion recognition depended significantly on kinematic and postural movement features such as limb contraction and vertical movement in monads and dyads, whereas in dyads recognition also relied on interpersonal proximity measures such as interpersonal distance. Thus, EBL processing in monads seems to undergo a similar developmental shift from a positivity bias to a negativity bias, as was previously found for emotional faces and terms. Despite these age-specific processing biases, children and adults seem to use similar movement features in EBL processing.