<p>This paper describes a semi-empirical methodology to estimate the future evolution of extreme sea level event frequency, combining the outputs of climate models, IPCC projections of the mean sea level in given scenarios, and the statistical distribution of extreme events deduced from observations. The methodology is applied under both extreme and mild scenarios to the case study of Trieste, in the northern Adriatic basin, for which over 100 y of observed sea level data from tide gauges are available. The climate model runs cover the period between 1987 and 2100. In this work we quantify extreme sea level events considering both the daily mean sea level, which mainly accounts for the role played by the atmospheric forcing, and the daily Highest High Waters, which allow us to directly assess the impact of the extreme sea level events on the urban environment. Our results show an increase in the frequency of such events mainly in connection to the mean sea level rise, while the atmospheric forcing appears to play a minor role. By the end of the 21st century the extreme sea level events are expected to become more than one order of magnitude more frequent than in the current climate. Despite substantial uncertainties in the estimated future frequencies, our findings point to a remarkably fast increase during the second half of the century, which raises the problem of a timely response and adaptation of the urban environment to the expected changes.</p>