Including animals in autism intervention is growing in both research and practice. A systematic literature review was conducted to collate and synthesize all empirical research on animal-assisted intervention (AAI) for autism published from 2012 to 2015. Findings from 28 included studies revealed that AAI programs generally include one animal per participant with a total contact time of approximately 10 hours over the course of 8 to 12 weeks. Research methodology is diverse and though limited in many cases, has improved over the last few years. The most commonly reported outcome was increased social interaction, which was unanimously significant across 22 studies. The need for further research is highlighted, calling for a focus on refining AAI techniques, identifying optimal circumstances for positive change as well as individuals who may not benefit, and independent replication of high quality studies to move AAI from an enrichment activity to an evidence-based practice for autism.