The experiments were conducted to investigate the effect of simulated acid rain on the germination and the growth of Amaranthusdubius Mart. ex Thell. The effect of simulated acid rain using sulphuric acid with different pH concentrations (2, 3 and 4) were determined by exposing the seeds and seedlings to them for ten consecutive days. A control (pH 6.8) was placed along with the treatments. The seed germination was found reduced at pH 2. The effect on seedlings showed remarkable reductions on the growth parameters and the chlorophyll content. A large number of reductions were noted at pH 2. The leaves were with marked irregular lesions, necrotic spots and chlorosis at pH 3 and pH 2 levels. The total phenol content showed an increasing trend as pH level reduced from 4 to 2. Thus this study points out that Amaranthusdubius Mart. ex Thell. has less tolerance to acid rain which demands new resistant varieties through breeding and other plant propagation methods.