Hurricane Sandy struck New York City on October 29, 2012, causing not only a large amount of physical damage, but also straining people’s health and disrupting health care services throughout the city. In prior research, we determined that emergency department (ED) visits from the most vulnerable hurricane evacuation flood zones in New York City increased after Hurricane Sandy for several medical diagnoses, but also for the diagnosis of homelessness. In the current study, we aimed to further explore this increase in ED visits for homelessness after Hurricane Sandy’s landfall. We performed an observational before-and-after study using an all-payer claims database of ED visits in New York City to compare the demographic characteristics, insurance status, geographic distribution, and health conditions of ED patients with a primary or secondary ICD-9 diagnosis of homelessness or inadequate housing in the first week after Hurricane Sandy’s landfall versus the baseline weekly average in 2012 prior to Hurricane Sandy. We found statistically significant increases in ED visits for diagnosis codes of homelessness or inadequate housing in the week after Hurricane Sandy’s landfall. Those accessing the ED for homelessness or inadequate housing were more often elderly and insured by Medicare after versus before the hurricane. Secondary diagnoses among those with a primary ED diagnosis of homelessness or inadequate housing also differed after versus before Hurricane Sandy. These observed differences in the demographic, insurance, and co-existing diagnosis profiles of those with an ED diagnosis of homelessness or inadequate housing before and after Hurricane Sandy suggest that a new population cohort—potentially including those who had lost their homes as a result of storm damage—was accessing the ED for homelessness or other housing issues after the hurricane. Emergency departments may serve important public health and disaster response roles after a hurricane, particularly for people who are homeless or lack adequate housing. Further, tracking ED visits for homelessness may represent a novel surveillance mechanism to assess post-disaster infrastructure impact and to prepare for future disasters.