Background: The study aimed to investigate the effect of nebulized 5% and 7% Hypertonic Saline (HS) versus Normal Saline (NS) in acute viral bronchiolitis.Methods: This is a prospective, randomized controlled trial study that has been done on 90 infants presenting with acute bronchiolitis. All infants divided randomly in three equal size and matched groups (n=30). Subjects received 4ml nebulized 5% and 7% HS along with 0.15mg/kg Adrenaline or 4 ml 0.9%NS every 6 hours from enrolment until hospital discharge. For all patients, clinical symptoms such as sputum, wheezing, retraction rate, heart rate, fever, crackle, irritability, week nutrition and breathing were recorded in baseline and length of wheezing, cough, and crackle, length of stay (LOS), fever and sputum based on days in the end of study. Collected data analyzed by statistical methods in SPSS.19.Results: At baseline, study groups were similar in demographic and clinical characteristics. The mean age of all patients was 5.5±3.6 months, and 59 (65.6%) were male. The length of cough and crackle, and the length of LOS in 5% and 7% HS groups was significantly lower than NS group.Conclusions: Among infants admitted to the hospital with viral bronchiolitis, treatment with nebulized 5% HS and 7% HS had significant effect on decreasing clinical symptoms length and LOS when compared with NS.