Rheumatoid arthritis (RA) is characterized by chronic inflammation in joints. Obesity, stress, being women, and dietary pattern are important in pathogenesis. The joint damage in RA is accelerated by oxidative stress. The aim of this study was to examine the serum total antioxidant level, nutritional status, and Mediterranean diet adherence of adult women with RA. 35 adult women RA patients and 35 healthy control subjects participated in this study (45.4 ± 11.61 and 42.5 ± 8.50 years, respectively). Nutritional status, physical activity levels, and adherence to the Mediterranean diet were questioned. Physicians assessed the disease activity score of patients with RA. Serum total antioxidant (TAS) and oxidant status (TOS) were analysed. The serum TAS of the control group was higher, whereas the oxidative stress index (OSI) and TOS were lower than that of RA group. Dietary protein, fiber, eicosapentaenoic acid (EPA), retinol, iron, zinc, and total antioxidant intake in the RA group were lower than the control group (p < 0.05). Individuals with higher fiber intake showed a significantly lower risk for RA after adjusted for potential confounding factors (OR = 0.845, 95% CI = 0.773-0.923, p < 0.001). The mean physical activity level of the control group was higher than that of the RA group (1.59 ± 0.10 and 1.53 ± 0.13, respectively) (p = 0.01). In conclusion, serum antioxidant parameters and dietary antioxidant intake are decreased in patients with RA. Therefore, medical treatment for these patients should be supplemented with medical nutrition therapy to achieve optimal nutritional status.