<p>Conventional dyeing processes release harmful chemicals into water, causing environmental and health issues. Microwave-assisted dyeing offers a solution by improving dye fixation, reducing chemical use, and lowering environmental impact. This study investigates the effects of microwave treatment on cotton dyeing with Reactive Blue 21. Both irradiated and non-irradiated dye solutions were applied to treated and untreated cotton fabrics, achieving high dye uptake under optimal conditions (75&#xa0;°C, 45&#xa0;min, pH 8, and aluminum acetate salt). FTIR and SEM analyses showed strong bonding and surface modification due to microwaves. ISO-standard evaluations rated dyeing as good to excellent, while a response surface model confirmed the importance of these conditions. Adsorption studies showed that the dyeing behavior aligned closely with the Langmuir isotherm (<i>R</i>² = 0.9928), and the thermodynamic study demonstrated a spontaneous, endothermic adsorption process and increased affinity of reactive dye on MW-treated cotton, as evidenced by positive values of entropy change (∆<i>S</i>^o), enthalpy change (∆<i>H</i>^o) and negative value of Gibbs free energy (∆<i>G</i>^o). Overall, the findings support microwave use in cotton dyeing for its energy, cost, and time-saving benefits.</p>