AIM To investigate the impact of fecal microbiota transplantation (FMT) treatment on allergic colitis (AC) and gut microbiota (GM). METHODS We selected a total of 19 AC infants, who suffered from severe diarrhea/hematochezia, did not relieve completely after routine therapy or cannot adhere to the therapy, and were free from organ congenital malformations and other contraindications for FMT. Qualified donor-derived stools were collected and injected to the AC infants via a rectal tube. Clinical outcomes and follow-up observations were noted. Stools were collected from ten AC infants before and after FMT, and GM composition was assessed for infants and donors using 16S rDNA sequencing analysis. RESULTS After FMT treatment, AC symptoms in 17 infants were relieved within 2 d, and no relapse was observed in the next 15 mo. Clinical improvement was also detected in the other two AC infants who were lost to follow-up. During follow-up, one AC infant suffered from mild eczema and recovered shortly after hormone therapy. Based on the 16S rDNA analysis in ten AC infants, most of them (n = 6) had greater GM diversity after FMT. As a result, Proteobacteria decreased (n = 6) and Firmicutes increased (n = 10) in post-FMT AC infants. Moreover, Firmicutes accounted for the greatest proportion of GM in the patients. At the genus level, Bacteroides (n = 6), Escherichia (n = 8), and Lactobacillus (n = 4) were enriched in some AC infants after FMT treatment, but the relative abundances of Clostridium (n = 5), Veillonella (n = 7), Streptococcus (n = 6), and Klebsiella (n = 8) decreased dramatically. CONCLUSION FMT is a safe and effective method for treating pediatric patients with AC and restoring GM balance.