This paper explores the effects generated by the Milan Expo 2015 on local hotels, with a particular focus on seasonality and operating performance. Four different seasonal periods are considered and ten hypotheses formulated. The analysis adopts a longitudinal approach based on STR data. The findings support an overall significant reduction of seasonality. The main effects relate to weak seasonal periods, when demand is predominately centered around only one segment. Concerning operating performance, occupancy, ADR, and RevPAR registered higher values in 2015, demonstrating significant growth when compared to previous years. RevPAR increased in all four periods, especially during the lowest seasonality (112%), triggered by occupancy (50%) and rate (41%). The case study also establishes a qualitative benefit, in that, within the three seasonalities, rates increased more than occupancy, thus improving financial margins. Finally, the Expo reduced the performance gaps between the four seasonal periods.