A new series of 7-O-substituted pyridyl-4 methyl coumarin derivatives were synthesized and characterized based on their spectral data. All the target compounds were evaluated for their in vitro antifungal activity against eight important fungal pathogens. This study showed that the introduction of the substituted pyridyl moiety at the 7-hydroxy position of coumarin could enhance the antifungal activities. It also indicated that a bulky substituent was not beneficial to the antifungal activity of those coumarin derivatives.