Some researchers suggest difficulties synchronising with a partner could underpin the social differences associated with Autism Spectrum Condition, potentially acting as a marker for autism. Social Motor Synchrony (SMS) is one aspect of synchrony that could augment observational diagnostic procedures. However, the full breadth of literature examining SMS in autism has not been systematically reviewed. A systematic review following the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines yielded 29 papers meeting inclusion criteria. Of 21 studies including a comparison group, all indicated weaker SMS between two autistic partners and in mixed-neurotype partnerships compared with two non-autistic partners. Papers involving mixed-neurotype pairs without a comparison group showed higher than chance SMS and demonstrated an increase in SMS over time following rhythm-based interventions. Although research so far demonstrates weaker SMS in pairs involving an autistic partner compared with non-autistic pairs, we identified several limitations which may have influenced SMS in autistic people and their partners. Further work is needed with autistic partnerships, more natural and preferred tasks within comfortable settings and partnerships, and more work to identify the basis of synchrony differences. We set out implications for design of further research.