Alcoholic steatohepatitis is an important medical problem but its effective therapies are still not available. Plant polyphenols are widely used for prevention of toxic liver damages. The aim of the study was to evaluate the hepatoprotective mechanism(s) of a cranberry peel polyphenol-rich extract, focusing on the effects of the polyphenols on the mitochondrial function.The main components of cranberry peel phenolic compounds were anthocyanins, flavan-3-ols, procyanidins, flavonols, phenolic acids, as was detected using UHPLC-ESI-QTOF-MS. The treatment of rats receiving ethanol (4 g/kg bw, 8 weeks) with cranberry polyphenols (daily, 4 mg/kg bw) partially prevented alcoholic liver damage, ameliorating steatosis and inflammatory signs in the liver, decreasing serum and liver triglyceride contents, ALT and AST activities, as well as diminishing TNFα and TGFβ levels in serum. The polyphenols inhibited Ca2+ - induced mitochondrial permeability transition, free radical generation in mitochondria during intoxication. The polyphenols (25 µg/ml) prevented mitochondrial oxidative impairments in vitro. In conclusion, the cranberry peel polyphenols with antioxidant properties exerted a hepatoprotective and anti-inflammatory effects in the model of alcoholic steatohepatitis via prevention of liver mitochondria dysfunction.