Immunosuppressive and antibacterial regimens in children after liver transplantation create a gut microflora imbalance that can be indirectly measured by the activity of fecal enzymes. The aim of this study was to specify the influence of diet supplementation with probiotic Lactobacillus casei DN on the activity of beta-glucuronidase, beta-glucosidase, and urease. Twenty-five children after liver transplantation (13 girls, 12 boys) ages 3 to 17 years were enrolled in the study. Two months after bacteria application the levels of all 3 enzymes decreased, reaching statistical significance for beta-glucuronidase and beta-glucosidase. Complete rebound in enzyme activity was observed months after the end of probiotic supplementation. We concluded that Lactobacillus casei DN-114001 consumption decreased fecal enzyme activity, a beneficial effect limited to the period of bacteria intake.