This study evaluates the impact of physicochemical parameters on aquatic insect diversity of Fateh Sagar Lake by assessing water quality across five sampling sites. Physicochemical parameters such as temperature, pH, total hardness (TH), total dissolved solids (TDS), dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were analyzed. The results indicated that while most physicochemical parameters remained within permissible BIS/ICMR standards, Site 5 exhibited signs of pollution with higher BOD and COD levels and lower DO. A total of 3668 aquatic insects from 65 species, categorized under 37 families and five orders, were recorded. The BMWP and ASPT indices were employed for biological assessment, revealing good water quality at Sites 1-3, moderate conditions at Site 4, and significant degradation at Site 5, where no aquatic insects were found. Statistical correlations highlighted the importance of DO in species composition and the influence of physicochemical factors on aquatic biodiversity. This study underscores the necessity of regular monitoring and conservation efforts to mitigate anthropogenic impacts on Fateh Sagar Lake.