BACKGROUND: Immunosuppressant administration subsequent to organ transplantation exerts a substantial influence on gut microbiota composition, thereby affecting patients' prognosis and quality of life. METHODS AND RESULTS: We conducted a retrospective analysis involving 18 patients who experienced severe diarrhea or recurrent urinary tract infection (rUTI) due to prolonged immunosuppressant usage after kidney transplantation. Following episodes of severe diarrhea or rUTI, these individuals underwent fecal microbiota transplantation (FMT), resulting in notable alleviation of clinical symptoms. No unexpected adverse or serious adverse events were reported. In comparison to the pre-FMT period, the α-diversity of the intestinal microbiota in patients did not exhibit a significant difference following FMT; however, there was a notable distinction in the β-diversity and analysis of similarity (ANOSIM). In addition, our findings indicated a significant decline in the relative abundance of the bacterial genera Veillonella, Enterococcus, and Oribacterium, whereas a marked elevation was observed in the relative abundance of Faecalibacterium, Roseburia, Sutterella, Parasutterella, and Ruminiclostridium 5 after FMT in patients. Furthermore, there was a notable alteration in the metabolic pathway of gut microbiota in patients following FMT, with a significant enrichment observed in pathways such as Flavone and flavonol biosynthesis, Cytoskeleton proteins, Chromosome-related processes, NOD-like receptor signaling pathway, Progesterone-mediated oocyte maturation, and Antigen processing and presentation. CONCLUSION: FMT exhibited an effective approach for managing rUTI and diarrhea arising from postoperative immunosuppressant exposure in kidney transplant recipients.