This study investigates the spatiotemporal distribution and removal efficiency of six neonicotinoid insecticides in the Prado Wetlands, a large-scale constructed wetland system in Southern California. The wetlands receive urban runoff and wastewater effluent, which are sources of neonicotinoid contamination. The total neonicotinoid concentrations in water ranged from 3.17 to 46.93 ng L\(^{-1}\), with imidacloprid and dinotefuran being the most frequently detected compounds. The removal efficiencies based on concentration and mass flux were calculated for different wetland cells, showing that the entire wetland train had a 61.3% removal efficiency. Principal component analysis revealed that pH and temperature were the primary factors affecting neonicotinoid removal. The study highlights the effectiveness of constructed wetlands in removing neonicotinoids through plant uptake, photolysis, and microbial degradation, providing valuable insights for managing neonicotinoid contamination in surface waters.This study investigates the spatiotemporal distribution and removal efficiency of six neonicotinoid insecticides in the Prado Wetlands, a large-scale constructed wetland system in Southern California. The wetlands receive urban runoff and wastewater effluent, which are sources of neonicotinoid contamination. The total neonicotinoid concentrations in water ranged from 3.17 to 46.93 ng L\(^{-1}\), with imidacloprid and dinotefuran being the most frequently detected compounds. The removal efficiencies based on concentration and mass flux were calculated for different wetland cells, showing that the entire wetland train had a 61.3% removal efficiency. Principal component analysis revealed that pH and temperature were the primary factors affecting neonicotinoid removal. The study highlights the effectiveness of constructed wetlands in removing neonicotinoids through plant uptake, photolysis, and microbial degradation, providing valuable insights for managing neonicotinoid contamination in surface waters.