To assess whether dementia is an independent predictor of death after a hospital emergency department (ED) visit by older adults with or without a COVID-19 diagnosis during the first pandemic wave. We used data from the EDEN-Covid (Emergency Department and Elderly Needs during Covid) cohort formed by all patients ≥65 years seen in 52 Spanish EDs from March 30 to April 5, 2020. The association of prior history of dementia with mortality at 30, 180 and 365 d was evaluated in the overall sample and according to a COVID-19 or non COVID diagnosis. We included 9,770 patients aged 78.7 ± 8.3 years, 51.1% men, 1513 (15.5%) subjects with prior history of dementia and 3055 (31.3%) with COVID-19 diagnosis. 1399 patients (14.3%) died at 30 d, 2008 (20.6%) at 180 days and 2456 (25.1%) at 365 d. The adjusted Hazard Ratio (aHR) for age, sex, comorbidity, disability and diagnosis for death associated with dementia were 1.16 (95% CI 1.01-1.34) at 30 d; 1.15 at 180 d (95% CI 1.03-1.30) and 1.19 at 365 d (95% CI 1.07-1.32),  < .001. In patients with COVID-19, the aHR were 1.26 (95% CI: 1.04-1.52) at 30 days; 1.29 at 180 d (95% CI: 1.09-1.53) and 1.35 at 365 d (95% CI: 1.15-1.58). Dementia in older adults attending Spanish EDs during the first pandemic wave was independently associated with 30-, 180- and 365-day mortality. This impact was lower when adjusted for age, sex, comorbidity and disability, and was greater in patients diagnosed with COVID-19.