Zero-valent iron nanoparticles were synthesized, for removal of Direct Yellow 12 dye. The experiments were designed by response surface methodology. Quadratic model was used to predict the variables. Analysis of variance was used for investigation of variables and interaction between them. High F-value (10.01), very low P-value (<0.0001), non-significant lack of fit, the determination coefficient (R2 = 0.903) and the adequate precision (10.82) demonstrate good correlation between experimental and predicted values of the response. The highest removal percent (90.02%) was attained, and the optimum parameters are achieved: catalyst amount (0.31 w/w%), initial concentration (40 mg/l), reaction time (105.35 s) and pH (5.23).