Background & Aim: The aim of this study was to assess the antifungal effect of the watercress extract on the growth of Fusarium solani, the causal agent of potato dry rot.Experimental: This research was done in a completely randomized design with three concentrations and four replicates on potato dextrose agar (PDA) culture medium.Results: Results of this study indicated that all concentrations of alcoholic extract of watercress can significantly inhibit mycelia growth of Fusarium solani on PDA medium. Among different concentrations of watercress extract, the highest inhibition zone of the fungus (26.1 mm in diameter) was obtained at dose of 600 mg/ml. The rate of growth inhibition was concentration dependent. However, no significant difference in the rate of growth inhibition of the fungus by watercress extract was seen between the 500 mg/ml and 400 mg/ml or between 400 mg/ml and 300 mg/ml of the plant extract.Recommended applications/industries: The overall results of this experiment indicated that the alcoholic extract of watercress can inhibit mycelia growth of Fusarium solani in a dose dependent manner. It seems therefore, that the watercress extract has the potential to be employed for manufacturing natural fungicidal compounds. It is recommended that the experiment to be tested on potato tubers (in vivo conditions). پرونده مقاله