Aim Emergency department (ED) doctors are under time pressure to expedite decision‐making. This task would seem more difficult in older patients who present atypically, have multiple comorbidities and require more diagnostic tests. This study aimed to investigate the rate of appropriate initial diagnosis of older ED patients admitted under medical units, and whether time was a factor. Methods Retrospective review of all patients admitted under medical units from ED over a one‐month period was conducted. Results Four hundred ninety‐three records were reviewed. Mean time to ED review was 87 minutes, and to medical registrar review, 409 minutes. Overall rate of appropriate initial diagnosis made by ED was 85.8%, with significantly lower rate detected in older patients. Overall rate for medical registrar was 94.5%. Conclusions Admitted older ED patients received lower rates of appropriate initial diagnosis. Time may be a contributing factor to this lower rate. Length of stay was prolonged if initial diagnosis was inappropriate.