Sodium salt of Montelukast is the leukotriene receptor antagonist used for the treatment of asthma and allergies. LC-MS/MS method was developed to determine Montelukast sodium in human plasma. The quality control samples were prepared between 100 and 12000 ng/mL. Plasma concentration samples were prepared in between 2.5 ng/mL and 600 ng/mL. The method was found to be linear in the range of 2.5 ng/mL and 600 ng/mL.The concentration vs. ratio of Montelukast sodium/ IS has y = 0.004x + 0.135 with R2= 0.991.The procedure followed in this method has the least concentration i.e. LLOQ is very low than previously reported methods and is suitable for estimation of Montelukast sodium in human plasma.