Faecal microbiota transplantation (FMT) is currently a recommended therapy for recurrent/refractory Clostridioides difficile infection (CDI). The success of FMT for CDI has led to interest in its therapeutic potential in many other disorders . The mechanisms that underpin the efficacy of FMT are not fully understood . Importantly, FMT remains a crucial treatment in managing CDI and understanding the mechanisms that underpin its success will be critical to improve its clinical efficacy, safety and usability . Furthermore, a deeper understanding of this may allow us to expose FMT ’ s full potential as a therapeutic tool for other disease states . This review will explore the current understanding of the mechanisms underlying the efficacy of FMT across a variety of diseases.