The objective of the paper was to determine the effect of industrially produced concentrate of acidwhey (obtained during the making of cottage cheese) on technological properties and quality of bread. Baking wheat products were made using a wheat flour of type 500 or 750, whereas wheat-rye breads (known as the Baltonowski bread) were made from mixed wheat and rye flours: wheat flour of type 750 and rye flour of type 720. In the phase of making dough for bread, a spray-dried acid-whey concentrate was added into it in the amount of 20 or 30%. A significant increase in the dough and bread yield was found to be the effect of the acid-whey addition. Compared to control samples, the experimental bread loaves showed a decrease in their unit volume. Owing to the content of acid-whey concentrate in the breads, the colour of their crumbs was evidently brighter, and the crust colouration was more intense. In the experimental breads, statistically significant increases in the content of nutritive components, proteins, and total mineral components were reported.