Many azo compounds are known for their antifungal property. In the present study, synthesis of 1-phenylazo-2-naphthol (C₁₆H₁₂N₂O) was carried out as an azo coupled dye through coupling reaction of phenyl diazonium salt and β- naphthol in ice-cold chilled water. The azo coupling preferably occurs at ortho position of the same ring since the charge density get reinforced at this position. The 1-phenylazo-2-naphthol-naphthol was characterized through FTIR. The antifungal activity was tested against a highly problematic soil-borne plant pathogen Sclerotium rolfsii. The compound was dissolved in dimethyl sulfoxide (DMSO) and mixed with malt extract broth to prepare 6 mL of 100 mg mL^-1 growth medium. Its concentrations in the range of 0.78 to 100 mg mL^-1 were tested against the fungal pathogen. None of the concentration was found antifungal. In contrast, all the concentrations increased the fungal biomass to variable extents ranging from 0 to 29%. This study concludes that 1-phenylazo-2-naphthol does not possess antifungal property against S. rolfsii.