The objective of this research was to investigate the effect of different ratios of whey protein concentrate (WPC) conjugated with galacto-oligosaccharide (GOS) as 2:1, 1:1, and 1:2 and different reaction times (0, 2, 4, and 6 h) on the structural characteristics and functional properties of the WPC-GOS conjugates. The WPC was glycated with GOS via the Maillard reaction using wet-heating treatment. The color development, SDS-PAGE, FTIR, microstructure analysis, and functionality of the WPC-GOS were determined. A glycation degree of up to 30-35 % was achieved after the reaction between WPC and GOS, and treated mixtures WPC-GOS clearly developed color changes due to the Maillard reaction. The WPC-GOS ratios of 1:1 and 1:2 at 4-6 h showed improvement in emulsifying property, and foaming stability. The antioxidative properties of the WPC-GOS conjugate were also significantly enhanced 2-fold at 6 h (inhibition of DPPH, ABTS), 1:2 showed the highest ferrous reducing power (10.12 µmole/g) followed by 1:1 (9.03 µmole/g) and 2:1 (8.89 µmole/g) under the same heating time. This conjugation can be further advantageous in developing food ingredients and novel materials for prebiotic and bioactive compounds.