The purpose of this study was to investigate the effect of Manganese ions (Mn2+) on colour development of ninhydrin by alendronate for the spectrophotometric analysis of alendronate sodium in tablets. The analysis was based on the reaction of ninhydrin with the primary amino group in alendronate in the presence of 0.01 M sodium bicarbonate solution and microgram quantity of Mn2+ ions. The mixture was heated in a water bath at 95 ± 5°C for 35 min, and then cooled down at room temperature for 10 min. The absorbance of the purple-colour complex was measured against reagent blank at 568 nm. The method was found to be linear in the range of 2-12 μg/ml-1 and the correlation coefficient was 0.9997. Limit of quantification was found to be 1.4 μg/ml-1. Mean percentage recovery was found to be 99.73 ± 1.33%. The validated method was used for the quantification of alendronate in tablets. Tablet excipients showed no interference with the analysis and percentage of labeled amount was found to be 100.07 ± 1.2%. The proposed spectrophotometric method is suitable for the routine analysis of alendronate in tablets.