Whey is a by-product in the dairy industry and it is characterized by nutritional values and health benefits; however, if unmanaged, it poses a serious danger to the environment. The steadily increasing production of cheese and, consequently, of whey makes it necessary to search for new methods of utilizing whey, mainly in the food industry. One of the options is the production of probiotic fermented beverages containing whey. Of the probiotic strains applied to the fermented milk beverages production, Lactobacillus acidophilus bacteria are those that are very often used. The objective of this research study was to determine the quality of fermented beverages containing the L. acidophilus La-5 probiotic strain made from frozen acid whey mixed with milk in the ratio 1:1. Four variants of beverages were produced: N without functional additives; NO containing oligofructose; NW with a WPC 35 whey protein concentrate; and NOW with oligofructose and WPC 35; all of them were stored under refrigerated conditions for a period of 14 days. After the 1^st, 7^th, and 14^th day of storage, their organoleptic properties, acidity, and the content of acetal aldehyde were determined as was the number of L. acidophilus therein. It was found that all the variants of beverages were characterized by a very good or good taste and smell; however, the apparent syneresis was their disadvantage. During the storage, there were reported an increase in the acidity and a decrease in the content of acetal aldehyde. During the entire period of storage, the number of viable probiotic bacteria was high and significantly exceeded a level of 10⁶ cfu /cm³, i.e. the minimum level as required by WHO in the probiotic products.