The aim of this study was to investigate the effect of the implementation of an antibiotic stewardship program (ASP) on antibiotic consumption in our 428-bed hospital. The Infection Control Committee implemented an ASP beginning in January 2016, aiming to reduce inappropriate antibiotic use through improved prescribing practices. The ASP included both pre-authorization and prospective audit and feedback strategies. We collected pharmacy and hospital data for the years 2015 (pre-intervention) and 2016 (post-intervention). Consumption data were expressed as daily defined doses (DDDs) per 100 patient-days (PD) and the significance of the differences between 2015 and 2016 was assessed by paired t-test. Antibiotic resistance rates for the most important hospital pathogens were monitored for 2015-2016. The ASP effectively reduced consumption of most antimicrobials; total antibiotic use decreased by 16.7% (from 104.3 in 2015 to 86.9 DDDs/100 patient-days in 2016, p < 0.001) owing to reduction of 19.1% for non-restricted and 13.8% for restricted antibiotics. Important restricted antimicrobials, such as colistin, carbapenems, quinolones and tigecycline showed significantly decreased usage post-intervention. Significant changes in the resistance rates were not observed, except a decreasing trend for colistin and tigecycline (Acinetobacter baumannii and Klebsiella pneumoniae) and also vancomycin (enterococci). The ASP was successful in terms of reducing the antibiotic consumption for the first year of its implementation. Interestingly, antimicrobials requiring pre-authorization exhibited a lower reduction than other antibiotics. Potential effects of the ASP in reducing resistance rates remain to be shown.