Fecal microbiota transplantation (FMT) is an effective therapy for recurrent Clostridioides difficile infection and is increasingly being explored for other microbiota-associated diseases. However, general research has largely focused on bacterial engraftment, overlooking the contribution of the gut virome. In this perspective, we highlight phage-mediated horizontal gene transfer (HGT) as a potentially influential process occurring following FMT. Donor-derived phages may potentially influence community structure, engraft in resident bacteria, and modulate microbial functions or host physiology. In addition, temperate phages are well-equipped to mobilize bacterial genes, such as metabolic functions, stress-response traits, and antibiotic resistance determinants, raising the possibility that gene flow could well contribute to FMT outcomes. We propose a conceptual model in which phages act as bidirectional mediators of adaptation, not only accompanying bacterial communities b...