The complex nature and the manufacturing process of poly(dl-lactide-co-glycolide) (PLGA), a key component of PLGA-based microspheres, have made the quantification of this copolymer difficult. The main purpose of the current study was to investigate the potential of three different methods for the quantitative analysis of the PLGA content of clinical products. In this regard, leuprorelin acetate microspheres from different vendors were chosen as templates to validate quantitative 1H nuclear magnetic resonance (qHNMR) spectroscopy, size exclusion chromatography (SEC), and high-performance liquid chromatography (HPLC) methods qHNMR proved to be an excellent and rapid PLGA quantification method compared to the other two. The recovery value was 99.12% and the linearity correlation coefficient was 0.9999. The results obtained from the qHNMR method were found to match the data provided by the vendor, suggesting that qHNMR can be utilized as a reliable quality control and inspection tool for PLGA-based clinical products.