Firocoxib is a non-steroidal anti-inflammatory drug specifically formulated for veterinary medicine and selectively acts on inhibiting the cyclooxygenase 2 enzyme(COX-2). This study aimed to evaluate the possible adverse effects of administering oral therapeutic firocoxib on gastric mucosa, hematological parameters, coagulation cascade, and hepatic and renal biochemistry in healthy horses. Nine clinically healthy Arabian horses, approximately nine years old, received 0.1mg/kg of oral firocoxib for 14 days. Before beginning treatment, a gastroscopic examination was conducted, and venous blood samples were obtained for laboratory tests on D0. Follow-up blood samples and gastroscopic examinations were taken on D7 and D14 after starting treatment and one week after completing treatment on D21. No changes were found in the gastroscopic and hematological tests. Additionally, coagulation and serum biochemistry levels remain between normal values for this particular species. However, the increased activated partial thromboplastin time (aPTT) and prothrombin time (PT) indicate reduced blood coagulation capacity, which contradicts the expected effect of treatment with selective COX-2 inhibitors, as these drugs theoretically promote coagulation. Administering Firocoxib to horses is safe as it does not cause any significant adverse reactions. Therefore, it is a suitable option for managing inflammatory conditions in these animals.