This study was aimed at using nanofiltration to purify the galactooligosaccharides (GOS) found in a commercial mixture containing lactose, glucose and galactose, whose compositions were similar to that obtained through transgalactosylation reactions catalysed by β‐galactosidase from Kluyveromyces marxianus CCT 7082. NP030 polyethersulphone membrane was selected for the purification processes, once it differed statistically from other membranes due to the higher purification factor and permeate flux under the optimised temperature and pressure conditions of 35 °C and 3 MPa, respectively. Results indicate that NP030 membrane can be employed as a preliminary technique for the GOS purification with approximately 61% (w/w) of recovery Ver menos