Photocatalysis is an unconventional, but promising method that can reduce industrial wastewater pollution, especially in the textile industry by decomposing toxic dye waste into harmless parts under suitable irradiation sources. Cationic dyes are synthetic textile dyes that are toxic and difficult to degrade, so they need to be treated properly. An effective method for removing harmful organic dyes is photocatalytic. This study aims to synthesize and characterize ZnO/MnFe2O4 nanocomposites and to study the effect of variations in the ratio of ZnO: MnFe2O4, pH, dose, irradiation time on band gap reduction, and photocatalytic applications tested with cationic dyes, namely methylene blue using sunlight as a light source. The synthesis of nanocomposites using the co-precipitation method with variations in the mole ratio of ZnO:MnFe2O4 1:0.1; 2:0.1; 3:0.1. Based on the experimental results, the results of the characterization of XRD, SEM-EDX, FTIR, and BET proved that the component forming the nanocomposite is ZnO/MnFe2O4. The band gap measured using UV-DRS showed that decreasing ZnO would also decrease the band gap of the nanocomposite from 3.35 eV to 2.78 eV. For the degradation of 50 mg/L methylene blue (MB) dye, the highest degradation of 93.2% was obtained by using a catalyst dose of 20 mg at a ratio of 1:0.2 for 50 minutes of irradiation. The point of zero charge (pzc) obtained at pH of 7.9 which makes the solution pH 8 suitable for photodegradation adsorption.