Background: Visceral leishmaniasis is one of endemic illness in Iraq, and the immunosuppression is one and important clinical symptom of disease. Aim: The current study aims to measuring the level of IL-4 in patient with Kala-azar. Methods: 60 sample from patients with visceral leishmaniasis who were admitted to hospital that were let in the study from the period between September 2024 to march 2025, and other groups consist of 30 apparently healthy individuals. A five ml of blood samples were collected, for IL-4 ELISA test. Results: The Mean levels of Interleukin-4 were 1443.92 ± 112.67 and 946.13 ± 190.52, respectively, patients and healthy controls; the level (mean level) was significantly higher in patients with visceral leishmaniasis compared to healthy controls (P< 0.001). The present study confirmed the role of IL-4 in predicting kala-azar, demonstrating that 59 out of 60 patients (98.3%) had values exceeding the cutoff (>1236.55), whereas none of the healthy subjects (0%) had IL-4 levels above this cutoff. The difference is highly significant (P > 0.001). Analysis of the ROC curve indicates that the IL-4 cutoff value is >1236.55, with sensitivity, specificity, PPV, and NPV rates of 98.3%, 100.0%, 100.0%, and 96.8%, respectively. Conclusion: a significant association between serum IL-4 levels in patients with Kala-azar.