Community-acquired pneumonia is a prevalent disease in the Emergency Department (ED). The literature reveals that clinical practice could not be related with guideline recommendations. The aim of this study is to determine the impact of the implementation of the recommendations of the Spanish Society of Emergency Medicine in the Hospital Clínico Universitario Lozano Blesa (Zaragoza) ED in the management of community-acquired pneumonia. Use of Pneumonia Severity Index (PSI) estimation was used to assess the adherence. This study was carried out from December 2014 to February 2015. Data was compared with the previous two months. The indicators management (discharge or admission decision, adequacy and anti-biotherapy) as well as the incidence of PSI estimation before and after the intervention in these parameters were evaluated. 209 patients were included, 97 before the intervention and 112 after the intervention. No significant differences were observed in the calculation of PSI. A significant decrease in admissions was observed after the intervention in the patients in whom the PSI was calculated (68.8% vs. 45.0%, p<0.05). A greater use of the Observation Room was aimed at those patients in whom the PSI was calculated (06.3% vs. 17.5%, p<0.05). PSI calculation significantly increased antibiotic prescription adherence (88.9% vs. 75.2%, p<0.05). There were no modifications in the prescription after the intervention. In conclusion, PSI is a useful and effective measure to achieve greater adherence to the recommendations. However, despite the positive trend in the use of the PSI and its interpretation, a low-intensity intervention is not sufficient to generalize its use.