Kinetics and mechanism for alkaline hydrolysis of C. I. Disperse Blue 284 (B-284) which is dulitrothiophene azo disperse dye were investigated. On contacting with alkali, color strength of B-284 decreased instantly and continuosly. The hydrolysis rate of B-284 increased with increasing alkali, concentration and appeared following first order reaction. The observed rate constants obtained from hydrolysis of various amounts of the dye were similar and of initial rates calculated showed that B-284 hydrolyzed by first order reaction. Therefore it was confirmed that the overall reaction was second order, SN2 of nucleophilic substitution reaction. Increasing temperature enhanced the hydrolysis of B-284. From the results of hydrolysis performed at various temperatures, it was obtained that activation energy(E ) was 13.1 kcal/mole, enthalpy of activation($Delta$H) was 12.3 kcal/mole, and entropy of activation($Delta$S) was 20.0 EU,