Using the concept of the simultaneous equation approach, a precise, accurate, and economical method for estimating Montelukast sodium and Bilastine simultaneously in multiple tablet definite volumes has been developed. The methodology is based on measurements of bilastine at 282 nm and montelukast sodium at 287 nm in methanol. Numerous analytical parameters, such as linearity, precision, accuracy, and toughness, were established in accordance with ICH guidelines. The linearity of montelukast and bilastine at their respective wavelengths is demonstrated by their concentration ranges of 2–12 g/ml and 4–24 g/ml, respectively. Utilising statistics, the validity of the method was examined. The results of the montelukast sodium and bilastine analysis formulation, both 101.83% and 99.79% of label claims, were found to be true when expressed as a percentage.