Background: Older individuals are particularly prone to suffer health-care-related adverse events (AEs); they often have more comorbidity and, thus, require more health-care. Since our society is ageing, insight into AEs leading to hospital admissions is necessary. We aimed to assess the incidence, predictive factors and consequences of AEs leading to admission in older individuals. Methods: We performed a retrospective cohort study of all older patients (≥65 years) who were admitted through the emergency department (ED) to the department of internal medicine in the last week of every month in 2011. We retrieved the incidence and possible predictive factors for AEs leading to admission and mortality (both in-hospital and within 28 days after discharge). The control group consisted of older patients admitted because of other reasons. Results: In the study period, there were 262 admissions, of which 106 (40.5%) were because of an AE. The most common AE was medication-related (55.7%). Predictive factors of admission because of an AE were the number of medications used [odds ratio (OR) 1.16 per medication, 95% confidence intervals (CI) 1.08–1.25] and dependency in instrumental activities of daily living (IADL) (OR 0.35, 95% CI 0.14–0.91). Both in-hospital mortality and mortality within 28 days after discharge were lower in the AE group (5.7% vs. 16.0%, P = 0.01, and 0 vs. 6.9%, P < 0.05, respectively). Conclusion: Admissions through the ED to the department of internal medicine of older patients are often because of AEs (40.5%), with medication use being the greatest culprit. Surprisingly, mortality was lower in the AE group. The number of medications used (positive) and IADL dependency (negative) were predictive factors for being admitted because of an AE.