Background: Bronchiolitis is a leading cause of hospital admissions and death in young children. Clinical practice guidelines (CPG) to diagnose and manage bronchiolitis have helped healthcare providers to avoid unnecessary investigations and interventions and to provide evidence-based treatment. Aim of this study is to determine the effect of implementing CPG for the diagnosis and management of bronchiolitis in a tertiary hospital in Jordan. Methods: The study compared children (age <24 months) diagnosed with bronchiolitis and who required admission to King Abdullah University Hospital in Irbid during the winter of 2017 (after CPG implementation) and age-matched children admitted in the winter of 2016. The proportion of patients receiving diagnostic tests and treatments in the two groups were compared.Results: Eighty-eight and 91 patients were diagnosed with bronchiolitis before and after CPG implementation, respectively. Respiratory syncytial virus rapid antigen detection testing decreased after CPG implementation [n=64 (72.7%) vs n=46 (50.5%), p=0.002]. However, there was no significant change in terms of other diagnostic tests. The use of nebulized salbutamol [n=44 (50%) vs n=29 (31.9%), p=0.01], hypertonic saline [n=39 (44.3%) vs n=8 (8.8%), p<0.001], and inappropriate antibiotics [n=31 (35.2%) vs n=15 (16.5%), p=0.004] decreased after CPG implementation. There was no difference in mean LOS (standard deviation; SD) between the pre- and post-CPG groups [3.5 (2) vs 4 (3.4) days, p=0.19]. The mean cost of stay (SD) was 449.4 (329.1) US dollars for pre-CPG compared to 507.3 (286.1) US dollars for the post-CPG group (p=0.24).Conclusion: We observed that the implementation of CPG for bronchiolitis diagnosis and management helped change physicians’ behavior toward evidence-based practices. However, adherence to guidelines must be emphasized to improve practices in developing countries, focusing on the rational use of diagnostic testing, and avoiding use of unnecessary medications when managing children with a diagnosis of bronchiolitis.