This study focused on the impact of the treatment with the hypomethylating agent 5-Azacitidine on the redox status and inflammation in 24 MDS patients. Clinical and genetic features of MDS patients were recorded and peripheral blood samples were used to determine the activity of the endogenous antioxidant defense system (superoxide dismutase, SOD, catalase, CAT, glutathion peroxidase, GPx, and reductase, GRd, activities), markers of oxidative damage (lipid peroxidation, LPO, and advanced oxidation protein products, AOPP). Moreover, pro-inflammatory cytokines and plasma nitrite plus nitrate levels as markers of inflammation, and CoQ10 plasma levels, were also measured. Globally, MDS patients showed less redox status in terms of a reduction in the GSSG/GSH ratio and in the LPO levels, and increased CAT activity compared with healthy subjects, with not changes in SOD, GPx and GRd activities, and AOPP levels. When analyzed the evolution from early- to advanced stages of the disease, the GPx activity, GSSG/GSH ratio, LPO and AOPP increased, with a reduction in CAT. GPx changes were related with the presence of risk factors such as high-risk IPSS-R or mutational score. Besides, there was an increase in IL-2, IL-6, IL-8 and TNF-α plasma levels, with further increase of IL-2 and IL-10 from early to advanced stage of the disease. However, we did not observe any association between inflammation and oxidative stress. Finally, 5-azacitidine treatment generates oxidative stress in MDS patients, without affecting inflammation levels, suggesting that oxidative status and inflammation are two independent processes.