Introduction: Certain aqueous insoluble drugs had shown remarkably good solubilization in lipophilic environment. Among such drugs: ramipril, azithromycin and fluconazole showed improved solubilization using essential oil based microemulsion drug delivery system. In this study, we focused on the toxicity profile of the drug delivery vehicle - cinnamon oil based system in Oreochromis Mossambicus (Tilapia) fishes. Methods: Histopathology and biochemical parameters like proteins, carbohydrates, free amino acids, catalase, total reduced glutathione, glutathione s-transferase and superoxide dimutase were estimated in the drug delivery system with comparison to the control fishes. Results: At higher concentrations of the vehicle, significant changes were observed in the system as compared to control, which, could be due to stress factors or severe pathologic infections. Conclusions: The drug delivery vehicle showed drastic changes at extremely higher volumes of drug delivery vehicle when treated in Tilapia fishes. Hence, further studies have to be carried out in rodents to determine the safest limit by carrying out toxicity studies. Only then, this drug delivery system could be used for future applications in pharmaceutical medicine.