Dairy industry generates contamination due to whey dumping from the manufacture of coagulated products. Ultrafiltration technology has been extensively studied in acid whey; however, research on sweet whey ─which is obtained from the production of fresh white cheese (Campesino cheese)─ is scarce. The objective of this study was to concentrate sweet whey proteins by ultrafiltration and to evaluate the process conditions. A polyethersulfone membrane with a molecular weight cut-off of 10 kDa was used. The effect of volumetric concentration factor between 5 and 18, transmembrane pressure between 2.5 and 5 bar was evaluated on the permeate flow, protein retention coefficient, and retention yield using a response surface methodology. The process optimization was carried out in that same range. Protein and fat were concentrated and underwent ultrafiltration; however, a less stable system was obtained. A higher concentration of protein can result in more collisions between molecules, thus generating flocculation. Whey protein concentrates had 18.2% of total solids out of which protein represents 45%.