Social perception emerges early, occurs automatically, and is used ubiquitously in daily life. Understanding its neural underpinnings is critical to cognitive neuroscience. A region in the right posterior superior temporal sulcus (STS) that selectively supports social interaction perception has been found by contrasting brain responses to interacting and non-interacting point light displays across subjects. However, in naturalistic stimuli, both the left and right STS support social interaction perception. Are the left and right regions performing similar computations? In this work, we combined univariate and multivariate fMRI analyses to investigate the relationship between the left and right STS. We used point light displays to localize social interaction perception selective voxels in the STS (SI-STS) and examined their response to videos of two simple shapes engaged in helping or hindering actions. Despite prior reports of strong right lateralization, we find that there is indeed social interaction selectivity in the left STS, however there is more overlap between subjects and stronger selectivity for social interaction in the right SI-STS. Further, information about whether an interaction is positive (helping) or negative (hindering) can only be decoded from the right hemisphere SI-STS voxels. We also found that responses in right motion selective cortex (MT) and SI-STS are more similar to each other than the left MT and SI-STS, regardless of type of stimuli. In a follow up experiment with natural movies, we find functional connectivity between right and left SI-STS. Together these results suggest that right MT and SI-STS may work in concert to extract social interaction information but also indicate a more prominent role of the left STS in social interaction perception.