Background and study aim: Chickenpox is highly infectious, self-limiting disease, caused by varicella-zoster virus. Thrombocytopenia frequently complicates chickenpox. This study was conducted to assess the correlation between serum interleukin 10 levels and thrombocytopenia in adult chickenpox patients. Patients and Methods: Fifty patients of chickenpox complicated by thrombocytopenia were included in this study as a patient group. Fifty patients of chickenpox with normal platelet of comparable age, race and gender were identified as a control group. All patients were diagnosed by clinical picture of chickenpox and by presence of varicella - zoster virus immunoglobulin M (VZV IgM) in the patient blood. Estimation of complete blood count, kidney function tests, liver function tests, fasting blood sugar, and levels of cytokines IL-10 and TNF-α were done in both groups on the day of admission and day of discharge. Results: At time of admission, IL-10 levels were significantly higher in patients group than in control group, while TNF-α level were not significantly different between the two groups. At time of discharge, we observed a significant decline in IL-10 levels in the patients group as compared with time of admission. A negative correlation between IL-10 levels and platelet count was observed while no correlation was found between TNF-α and platelet count. Conclusion: IL-10 level could play an important role in development of thrombocytopenia in patients with chickenpox.