Abstract: The natural presence of lactic acid bacteria in fish may be of great interest in producing fermented fish products worldwide. The aim of this study was to characterization of Lactic Acid Bacteria (LAB) isolated from the intestines of various samples of the adult and young Rainbow Trouts (Oncorhynchus mykiss) of commercial farms in West Azarbaijan, Iran. All isolates were Gram-positive, catalase-positive bacilli and cocci that did not produce gas from glucose, H and L test positive in O/F medium. Most isolates were able to growth at 15 and 45°C. This isolates were divided into 2 groups by sugar fermentation patterns. Strain in the group 1 were placed in the clusters of the genera Lactobacillus and strain in the group 2 were placed in the clusters of the genera Enterococcus. Lactobacillus plantarum was the dominant member of population of lactic acid bacteria that isolated from the intestines, accounting for 9% of the isolates.