Vibrio harveyi is an emerging pathogen that causes mass mortality in a wide variety of marine animal species; however, it is still unclear which environmental determinants correlate V. harveyi dynamics and the bacterium-mediated death of marine animal life. We conducted a correlation analysis over a 5-year period (2003-2007) analysing the following data: V. harveyi abundance, marine animal mortality and environmental variables (seawater temperature, salinity, pH, chlorophyll a, rainfall and total viable bacterial counts). The samples were collected from a coastal area in northern Japan, where deaths of a marine gastropod species (Haliotis discus hannai) have been reported. Our analysis revealed significant positive correlations between average seawater temperature and average V. harveyi abundance (R = 0.955; P < 0.05), and between average seawater temperature and V. harveyi-mediated abalone death (R = 0.931; P < 0.05). Based on the regression model, n degrees C rise in seawater temperature gave rise to a 21(n)-fold increase in the risk of mortality caused by V. harveyi infection. This is the first report providing evidence of the strong positive correlation between seawater temperature and V. harveyi-mediated death of marine species.