<b><i>Background:</i></b> Evidence for what diseases occur more commonly in older people from a poor residential environment (PRE) is limited. <b><i>Objective:</i></b> We investigated characteristics, especially the underlying reason (disease) for visiting an emergency department (ED), of older people from a PRE in ED settings. <b><i>Methods:</i></b> A cross-sectional study was conducted on people aged ≥65 years who presented to the EDs of 2 hospitals in Okinawa, Japan, between 2015 and 2019. PRE cases were identified by searching relevant words, such as a house overflowing with garbage from hoarding or housing squalor (<i>gomi-yashiki</i> in Japanese), in electric medical records. Controls (2 controls per case) were randomly selected from those without a PRE, with both living at home and matching each PRE case for age and sex. Characteristics of interest between cases and controls were compared using a χ<sup>2</sup> test. <b><i>Results:</i></b> PRE cases (<i>n</i> = 67), compared with controls (<i>n</i> = 134), were more often transported by ambulance (79.1% vs. 61.9%; <i>p</i> = 0.01). A family member or relative (43.4%) or professional supporter (20.8%) called an ambulance for most PRE cases. PRE cases were more likely to visit the ED due to injury/fracture (16.4% vs. 8.2%), rhabdomyolysis (11.9% vs. 1.5%), undernutrition/dehydration (10.4% vs. 1.5%), and cancer (9.0% vs. 5.2%) than controls (<i>p</i> < 0.001). PRE cases had a higher prevalence of being underweight (35.4% vs. 14.9%), dementia (41.8% vs. 16.4%), decubitus ulcer (29.9% vs. 8.2%), living alone (73.1% vs. 23.1%), and receiving public welfare assistance (35.8% vs. 9.0%) than controls (all <i>p</i> ≤ 0.001). <b><i>Conclusion:</i></b> In EDs, older people from a PRE exhibited certain diseases and characteristics.
