Yes blackberries are a very great source of antioxidants including the antioxidant anthocyanins which can help prevent the damage that free radicals can cause.
Eating blackberries can help prevent many diseases and boost your immune system as well and blackberries are a great healthy snack to keep around.
Blackberries also contain phenolic compounds, such as ellagic acid, tannins, ellagitannins, quercetin, gallic acid, anthocyanins, and cyanidins which helps to improve your health.
Just avoid eating too many blueberries at a time because they can cause diarrhea.