The corrosion inhibition of an aqueous extract of bitter leaf on aluminium alloy in 0.5M hydrochloric acid solution at various temperatures and concentrations has been studied using weight loss measurement method. The influences of concentration, temperature and immersion period on the inhibition efficiency of the inhibitor system were investigated. It was found that the corrosion rate was significantly reduced in the presence of the natural inhibitor at all concentrations considered. The result also revealed the good inhibiting action of bitter leaf extract at optimum experimental conditions; acting as anodic type. The inhibitive action was satisfactorily explained by both thermodynamic and kinetic models.