Nowadays an increasing attention of public and private agencies to the sustainability performance of events is observed, since it is recognized as a key issue in the context of sustainable development. Assessing the sustainability performance of events involves environmental, social and economic aspects; their impacts are complex and a quantitative assessment is often difficult. This paper presents a new quali-quantitative method developed to measure the sustainability of events, taking into account all its potential impacts. The 2014 World Orienteering Championship, held in Italy, was selected to test the proposed evaluation methodology. The total carbon footprint of the event was 165.34 tCO2eq and the avoided emissions were estimated as being 46 tCO2eq. The adopted quali-quantitative method resulted to be efficient in assessing the sustainability impacts and can be applied for the evaluation of similar events.