Ethanol-producing dysbiotic gut microbiota could accelerate the progress of non-alcoholic fatty liver disease (NAFLD). Metformin demonstrated some benefits in NAFLD. In the present study, we tested the ability of metformin to modify ethanol-producing gut bacterial strains and, consequently, retard the progress of NAFLD. This 12-week study included forty mice divided into four groups (n= 10); normal diet, Western diet, Western diet with intraperitoneal metformin, and Western diet with oral metformin. Oral metformin has a slight advantage over intraperitoneal metformin in ameliorating the Western diet–induced changes in liver function tests and serum levels of different cytokines (IL-1β, IL-6, IL-17, and TNF-α). Changes in liver histology, fibrosis, lipid content, Ki67, and TNF-α were all corrected as well. Faecal ethanol contents were increased by the Western diet but did not improve after treatment with metformin although the numbers of ethanol-producingKlebsiella pneumoniae(K. pneumoniae) andEscherichia coli(E. coli) were decreased by oral metformin. Metformin did not affect bacterial ethanol production. It does not seem that modification of ethanol-producingK. pneumoniaeandE. colibacterial strains by metformin could have a significant impact on the therapeutic potentials of metformin in this experimental model of NAFLD.