Pesticides transported from agricultural land into freshwater ecosystems may adversely affect aquatic organisms and disrupt ecological balance. This study investigated the effects of two imidacloprid-based pesticides (Kingprid and Kingema) on Cladophora glomerata (L.) Kütz. collected from Zangilan district. This filamentous green alga was selected as a model organism due to its sensitivity to environmental changes and its ecological role as a primary producer in freshwater habitats. Chlorophyll content, cell viability, and structural alterations were evaluated as indicators of stress. The results showed that both pesticide formulations led to a marked decline in chlorophyll content and cellular viability, with the intensity of effects increasing under higher exposure levels. At lower exposure, only slight pigment fading and minor structural modifications were observed, whereas higher exposure resulted in pronounced discoloration, membrane damage, cytoplasmic shrinkage, and fragmentation of algal filaments. Comparative analysis indicated that Kingprid exerted a stronger toxic effect than Kingema across all observed parameters. One-way ANOVA confirmed statistically significant differences among the treatments (p < 0.001), demonstrating a clear relationship between pesticide exposure and algal response. These findings suggest that imidaclopridbased pesticides can negatively impact freshwater algal communities, potentially reducing primary productivity and altering ecosystem stability. The study highlights the importance of incorporating algal bioassays and bioindicator species into ecological risk assessment and environmental monitoring programs, particularly in regions with increasing agricultural activity, such as the Zangilan district.