Objective: This study compared the prevalence of homelessness in consecutive patients presenting to a metropolitan hospital ED measured via a prospective housing screen with the prevalence of homelessness determined via retrospective audit of hospital data. Factors that altered the odds of patients being homeless and service outcomes that differed were examined for screened patients. Methods: All patients presenting to the ED during a 7 day period in 2017 were invited to complete a housing screen. A retrospective audit of all ED presentations during the same period also occurred. Demographic (e.g. age, gender), clinical (e.g. reason for presentation, ED presentation history) and arrival mode (e.g. time, how arrived) predictors of homeless status were examined alongside care outcomes (e.g. ED length of stay, admission and 28 day re-presentation). Results: Of 1208 presenting patients, 504 were prospectively screened and 7.9% were homeless. This compared with 0.8% of ED presentations coded as homeless in the Victorian Emergency Minimum Dataset and 2.3% of the 704 non-screened patients identified as homeless using Victorian Emergency Minimum Dataset Usual Accommodation alongside primary diagnosis and registration address. Within the screened sample, homeless patients were more likely to be male, arrive by emergency ambulance/with police, have a psychosocial diagnosis, and be frequent presenters. Representation within 28 days occurred for 43% of homeless and 15% of not-homeless patients. Conclusions: Hospital ED administrative data substantially under-recognises the prevalence of homelessness in presenting patients. Standardised use of brief housing screens could improve identification of and provision of support to this often highly vulnerable population.