The aim of this work was to ascertain yeast contamination of raw herring, the processed products and manufacturing environment, and to evaluate biochemical peculiarities of dominant species of the isolated yeasts, which could have influenced the product quality. A total of 36 yeast strains were isolated from herring products, raw material and their production environment during the manufacturing process. These yeasts were identified as 8 species belonging to Saccharomyces, Candida, Pichia, Rhodotorula, Debaryomyces, Yarrowia yeast genera. Saccharomyces cerevisiae and Candida glabrata yeasts dominated in herring products. Candida blankii, Debaryomyces hansenii var. hansenii, Yarrowia lipolytica, and C. glaebosa yeasts were isolated from raw herring. The studies on contamination of the production room air, equipment, dishes, packing and other surfaces showed that the majority of samples were infected by Saccharomyces cerevisiae and Candida glabrata yeasts that were also found in the processed herring production. Research on enzymatic activity showed that yeasts Pichia membranifaciens and Debaryomyces hansenii var. hansenii exhibited proteolytic activity, while Yarrowia lipolytica – lipolytic activity. Based on the preliminary study results of assimilation and fermentation of carbon sources as well as proteolytic and lipolytic activities, this could have had the negative influence upon the product quality.