This study aimed to identify age groups vulnerable to flood fatalities and quantify their vulnerability by means of statistical methods. First, the study obtained data of 122 victims directly resulting from five flood disasters in the Philippines over the period 2010–2013 which was used to compare the number of flood fatalities in each age group with the population numbers. The chi-square goodness-of-fit test shows that only one age group, people aged ≥70, was vulnerable to flood fatalities. Vulnerabilities of people aged ≥70 and <70, respectively, were quantified in terms of mortality, i.e., the ratio of flood fatalities and affected people. This study obtained two lognormal distribution curves moderately describing histograms built with samples on the mortality of the two age groups. Based on probabilistic parameters of the selected lognormal distribution curves, the study concludes that people aged ≥70 have more than three times the vulnerability to the risk of flood fatality than people aged <70. It is also suggested that the age dependency ratio, which is widely used to consider demographic vulnerability in flood vulnerability studies, should not be applied to the Philippines.