Extreme sea levels are likely to increase in the future with an expected accelerated rise in mean sea level and through possible changes in storminess. Society is becoming more vulnerable to extreme sea levels due to considerable growth in human populations and economy at the coastal zone and this is particularly true for Western Australia, the fastest growing Australian state or region. This paper describes a novel approach used to estimate future changes in extreme sea level around the southwest coastline of Western Australia. Probabilities of extreme sea level for the present climate have been estimated using a 60 year hindcast of sea levels. The impact of climate change has been explored by adding a range of mean sea level rise projections to these probabilities. Estimates of possible future changes in recurrence intervals every decade over the 21st century are presented, showing that climate change has the potential to significantly reduce current average recurrence intervals and that the amount of reduction varies significantly around the coastline.