Oxidative stress and inflammation together play a crucial role in the obesogenic process, and imbalances in reactive oxygen species, free radicals and antioxidants have been reported as being major mechanisms underlying obesity-related co-morbidities. Obesity and oxidative stress may be present even within the first two decades of life, and chronic exposure to systemic inflammation may contribute to the onset and progression of cardiovascular disease and diabetes. Bioactive compounds present in blueberry have been shown to have many positive effects on human health. The present study was carried out in northern Italy on a population of 24 overweight and obese children (8–13 years), divided into three groups: the first consumed fresh blueberries, the second blueberry purée, while a third control group did not consume any blueberries. The children's anthropometric measures were taken and serum markers related to inflammation, CRP, ceruloplasmin, and complements C3 and C4 were measured during the eight weeks they ate either fresh blueberries or blueberry purée. BAP test (Biological Antioxidant Potential) values of the three groups were monitored throughout the entire study and correlated with inflammatory, metabolic and anthropometric markers. The results showed a higher increase in antioxidant levels in the group that ate fresh berries than in the group that ate purée, while the control group's BAP values decreased over the eight weeks of the study. Our results show that increased consumption of blueberries, hence antioxidant intake, may also have a positive effect on markers of inflammation and oxidative stress in overweight and obese patients during childhood.