The potential of Neolamarckia cadamba cellulose nanofibril (CNF) filter paper as an azo dye treatment in a crossflow filtration system was investigated. The water permeability analysis was performed to assess the suitability of the fabricated CNF filter paper for filtration. Three operating parameters, cellulose dosage ratio, initial pH and initial concentration of methyl orange (MO) dye were optimised by central composite design (CCD) and response surface methodology (RSM). The results indicated that the model successfully predicted the relationship between the CNF filter paper and MO dye, demonstrating a high colour removal efficiency of 97.28% and an optimum normalised flux of 0.9748. These values were obtained under optimal conditions of a 50:50 cellulose ratio, pH 4, and an initial MO concentration of 600 mg/L. Fouling analysis using the Wiesner and Aptel model suggested that cake layer formation occurred in two stages under the optimum conditions. Overall, the findings indicate that RSM is useful for identifying suitable operating conditions, and the CNF filter paper shows good potential as a filtration material for azo dye removal.