A sensitive, simple and reproducible spectrophotometric method is developed for the determination of Artesunate in pure and pharmaceutical formulation. The method is based on the conversion of artesunate to Dihydroartemisinin (a lactol) by acid hydrolysis and the subsequent reaction of the Dihydroatemisinin with Vanillin, a carbonyl compound, to form a hemiacetal product. This is an acid catalyzed nucleophilic, addition reaction. The chromogen generated absorbed the uv-vis light at 420nm. The absorbance of the chromogen varied proportionally with the Artesunate concentration. Beer’s Law is obeyed between the range of 2-6 μg/ml with a Linear coefficient of 0.9998. The molar absorptivity and Sandell sensitivity were 1.19X104 L/mol/cm and 0.0323μg/cm2 respectively. The limit of detection and quantification were 0.28μg/ml and 1.30μg/ml respectively. The intra and interday precision and accuracy expressed as percentage relative standard deviation and percentage relative error were ≤ 2. 73 and ≤ 1.93. The method was successfully used to assay Artesunate in tablets procured locally and the results when compared statistically with a pharmacopoeia method showed good congruence. The accuracy and applicability of the method was confirmed by performing recovery studies via standard addition method with the result showing no interference from pharmaceutical excipients.