Acid whey, resulting from the production of soft cheeses, is a disposal problem for the dairy industry. Few uses have been found for acid whey because of its high ash content, low pH, and high organic content, which requires costly waste treatment. In 2015, about 400 million pounds of cottage cheese curd was produced in the United States. This process results in acid whey disposal of over 18 million pounds of whey protein annually. The objective of this study was to explore the potential of recovery of whey protein from cottage cheese acid whey for use in yogurt applications. Cottage cheese acid whey and Cheddar cheese whey were produced from standard cottage cheese and Cheddar cheese make procedures, respectively. The whey was separated and pasteurized by high temperature short time (HTST) pasteurization and stored at 4°C. Food grade ammonium hydroxide was used to neutralize the acid whey to a pH of 6.4. The whey was heated to 50°C and concentrated using an ultrafiltration system equipped with 11 polyethersulfone cartridge membrane filters (10,000 kDa cutoff) to 25% total solids, 80% being protein. Skim milk was concentrated to 6% total protein. Nonfat, unflavored set-style yogurt made with acid whey protein (AWP) was compared with yogurt made with additional sweet whey protein (SWP) and yogurt made from skim milk concentrate (SM). Yogurt mix was standardized to protein, lactose, and fat of 6.00, 6.50, and 0.10% respectively, with 37% of the protein coming from the whey. Yogurt was fermented in 6-ounce plastic cups at 43°C to pH 4.6 and stored at 4°C. The experiment was replicated in triplicate. The yogurts were measured over a period of 8 weeks for pH, titratable acidity, whey separation, color, and gel strength. Trained panel profiling was conducted on d 0, 14, 28, and 56. Yogurt made with AWP had similar color and titratable acidity to those made with SWP (P > 0.05). Yogurt with AWP had higher values of syneresis, lower gel strength, higher sour taste and lower firmness and viscosity compared with yogurts made with SWP (P < 0.05). Both yogurts with AWP and SWP were distinct in sensory characteristics from the control yogurt made from SM and from each other. These results indicate that AWP can be used as an ingredient in yogurt.