Nutritional interventions can reduce complications associated with coronary artery disease (CAD) such as inflammation and oxidative stress. This small, preliminary study aimed to evaluate a Brazil nut‐enriched diet's effects on markers of oxidative stress and inflammation in CAD patients. Twenty‐five CAD patients (13 male, 63.3 ± 6.7 years, BMI of 29.3 ± 5.6 kg/m2) were randomised to receive one unit of Brazil nut (5 g) per day for 3 months and were compared to 17 CAD patients (8 male, 63.3 ± 8 years, BMI of 28.6 ± 4.8 kg/m2) who served as control. Peripheral blood mononuclear cells were isolated, processed and analysed for expression of the transcription factors nuclear factor kappa B (NF‐κB) and nuclear factor E2‐related factor 2 (Nrf2), which is involved with antioxidant synthesis, and the antioxidant enzyme NAD(P)H: quinone oxidoreductase 1 (NQO1) by quantitative real‐time polymerase chain reaction (PCR). Plasma thiobarbituric acid‐reactive substances (TBARS) and clinical parameters were also measured before and after supplementation. No significant differences were found in any of the analysed parameters. Supplementing the diet with one Brazil nut a day for 3 months did not mitigate inflammation and oxidative stress in CAD patients. A longer period of supplementation may be required for positive effects to be seen.