Background: The most common and most serious complication of varicella (chickenpox) in adults is pneumonia, which can lead to severe respiratory failure. Whether addition of corticosteroids to antiviral treatment benefits patients with varicella pneumonia is unclear. Objectives: To assess the effect of dexamethasone as adjunctive therapy for treatment of varicella pneumonia on the length of hospital stay, which might cause earlier resolution of varicella pneumonia. Patients and methods: Forty patients were diagnosed as varicella pneumonia and divided into two groups, the first one involved 20 patients who received dexamethasone and acyclovir, and the second one involved also 20 patients but they received placebo and acyclovir. We measured liver function test, kidney profile, complete blood count, blood glucose, C-reactive protein and the levels of interleukin-6 on the day of presentation, after 4 days of admission and on the day of discharge from the hospital. Result: The mean length of hospital stay in the dexamethasone group was 6.5 days compared with 7.1 days in the placebo group and was significantly different between two groups. The mean time of switching to oral administration of acyclovir was 3.4 days in the dexamethasone group and 4.2 days in the placebo group. The mean time of switching to oral was significantly lower in dexamethasone group than in placebo group. Conclusion: Adding of dexamethasone to acyclovir in patients with varicella pneumonia can reduce the length of hospital stay.