Pyriproxyfen (PPF), a well-known synthetic substance, acts as an analog of juvenile insect hormone and is persistently used as insecticides as well as larvicides across the globe.  At present, meager information is available about the potential threats of PPF in aquatic species.  Therefore, this study determined the toxico-pathologic effects of PPF in fish.  In the current trial, 60 fish (Labeo rohita) of the same age, size, and body mass were randomly divided into four groups (T0-T3) and kept separate in glass aquaria with 100L water.  Fish in groups T1-T3 were exposed to 300, 600, and 900µg/L of PPF concentrations for one month.  On days 10, 20, and 30 of the experiment, blood and other visceral organs were collected from each fish.  The findings revealed a variety of clinical ailments in treated fish and a significant (P<0.05) difference in the body weight of specific visceral organs.  The erythrocyte counts, hematocrit, and hemoglobin reduced significantly while total leukocyte counts, and neutrophils as well as liver, kidneys, and heart biomarkers values increased significantly (P<0.05) compared to unexposed fish.  At the microscopic level, different lesions in the liver including edema, necrosis, inflammatory exudate, and kidneys necrosis, edema, widening of Bowman's space and necrosis of tubules, brain microgliosis, hemorrhages, pyknosis of neurons, and degeneration and in heart (neutrophilic myocarditis, edema, disruption of cardiac myofibers) were observed in treated fish.  The results of our experimental study shed light on blood, serum biochemistry, and the potential microscopic risks of PPF in freshwater fish.