Due to high augmentation in population and low availability of land, the quantum of wastewater production has surged resulting in advancements in wastewater treatment systems. To cope under such stressful circumstances, moving bed biofilm reactor (MBBR) proves to be an upgraded treatment technology for industrial and municipal wastewater treatment. The present startup study has been carried out using a laboratory-scale aerobic MBBR with working volume of 25L for textile dye wastewater treatment having AnoxKaldnes K3 media at filling percentage of 50%. In order to acclimatize the microorganisms on textile dye wastewater, the startup of the reactor was carried out using lactose as readily degradable co-substrate with textile dye wastewater in different ratios at hydraulic retention time (HRT) of 24 h. The biofilm on the media was developed in 63 days duration and the reactor attained pseudo-steady state (PSS) in 185 days period. During PSS condition of the MBBR, the maximum chemical oxygen demand (COD) removal efficiency of 92% with mixed liquor suspended solids (MLSS) concentration of 4224 ± 22 mg/L has been achieved. The kinetic study for biodegradation of textile dye wastewater has also been carried out using the Monod growth kinetics. The values of bio-kinetic coefficients of yield of heterotrophic biomass (Y) and endogenous decay coefficient for heterotrophic biomass (K_d) recorded are 0.394 mgVSS/mgCOD.d and 0.087 day⁻¹, respectively. The values of specific substrate removal rate (k), Monod half saturation constant (K_s), and maximum specific growth rate for heterotrophic biomass (µ_max) are 0.024 mgCOD/mgVSS.d, 53.203 mg/L, and 0.0095 day⁻¹, respectively, demonstrating the suitability and healthy performance of MBBR for textile dye wastewater treatment.