Previous evidence suggests that certain types of nuts, when included in a healthy diet pattern, may provide health benefits. Therefore, we hypothesize that the consumption of cashew nuts associated with a healthy diet may enhance antioxidant defenses and improve anthropometric and body composition parameters in individuals with obesity. We conducted a 12-week randomized clinical trial, divided into 4 sessions, involving adolescents randomly assigned to receive either 30 g of roasted cashew nuts together with nutrition education (cashew nut group-CNG) or only nutrition education (control group-CG). The total number of participants who started the study was 142, with 77 in the CNG and 65 in the CG. Data on anthropometry, body composition, and oxidative stress were collected at baseline (0-week) and endpoint (12-week). The main post-intervention findings in the CNG showed decreases in waist circumference (WC), thiobarbituric acid reactive substances (TBARS) and total antioxidant capacity (TAC) at 60 minutes in the CNG, while neck circumference (NC) increased. However, the CG showed an increase in TBARS and percentage of lean body mass (LBM), along with reduction in TAC at 60 minutes. After 12 weeks, the consumption of cashew nuts seemed to assist in WC reduction, even without a decrease in other anthropometric parameters, thereby decreasing the cardiometabolic risk. Furthermore, the consumption of cashew nuts demonstrated the ability to decrease overall oxidative damage as assessed by TBARS, a finding that reinforces the effects of this nut consumption against systemic oxidative stress associated with obesity.