A simple, sensitive and economical spectrophotometric method has been developed for the estimation of valacyclovir in pharmaceutical dosage forms. The method is based on the formation of a orange red coloured azo product by the diazotization of valacyclovir followed by a coupling reaction with resorcinol. The absorbance of orange red coloured solution is measured at 440 nm against reagent blank. Beer’s law is obeyed in the concentration of 50-250 μg/mL of valacyclovir. Statistical analysis proves that the proposed method is reproducible and selective for the estimation of valacyclovir in bulk drug and in its tablet dosage form.