Introduction: Acute bronchiolitis (AB) is a common reason for admission to the pediatric emergency department (ED). Evidence has shown that most interventions do not change the natural course of the disease. Methodology: The aim of this study was to evaluate the economic impact of the non-compliance with the AB Portuguese national clinical guideline (CG). A retrospective study of pediatric emergency episodes (EP) of a Portuguese hospital that had a diagnosis of AB during 2019 was conducted. Results: The sample included 344 EP. Non-compliance with the national CG occurred in 71,8% of the episodes, mostly due to unjustified treatment. Following GC in the studied ED for one year would have resulted in an estimated overall 76,6% cost reduction, with a reduction in mean direct costs (MDC) per patient of 14,93 \euro, corresponding to a medium saving of 3,89 \euro for each patient and a reduction of 11,03 \euro for the Portuguese National Health Service (NHS). Analyzing the unjustified MDC, of these 2,97 \euro were related to DT and treatment in the ED and the remaining 11,96 \euro were related to outpatient therapy. MDC imputed to the patient for outpatient treatment represented only 3,31 \euro, in this sense most of MDC is paid by the NHS. Conclusions: Compliance with GC would allow the reduction of total estimated costs by about 76.6%, representing a waste of resources, without compromising the quality of care provided. Most of the cost associated with non-compliance with the CG is justified by outpatient therapy, 67% of which was paid by the NHS.