Background <p>Poststroke outcomes remain highly variable, particularly in older and frailer patients with multiple comorbidities. This study aimed to evaluate the independent impact of prestroke cognitive status and comorbidities on one-year functional and vital outcomes.</p> Methods <p>Stroke patients (&gt; 50&#xa0;years old) were prospectively identified from the population-based Dijon Stroke Registry, France (2017–2022). Prestroke cognitive status (normal cognition, mild cognitive impairment (MCI), and dementia) and comorbidities were collected. Functional outcome (modified Rankin Scale) and survival were evaluated at 1&#xa0;year. Multivariable logistic and Cox regression models were used to assess the associations between cognitive status and patient outcomes.</p> Results <p>Among 1445 included patients (mean age 78.9 ± 12.0&#xa0;years; 53.4% women), 907 (62.8%) had no prestroke cognitive impairment, 241 (16.7%) had MCI, and 297 (20.5%) had dementia. Patients with preexisting cognitive impairment were older and had a higher prevalence of vascular risk factors and comorbidities. One-year case-fatality was 25.7% in cognitively unimpaired patients, 35.3% in MCI patients, and 59.3% in patients with dementia. A poor functional outcome was observed in 49.9%, 66.2%, and 81.4% of patients, respectively. After adjustment for comorbidities, both MCI (OR = 1.45; 95% CI 1.01–1.81, <i>p</i> = 0.04) and dementia (OR = 2.65; 95% CI 1.81–3.87, <i>p</i> &lt; 0.001) were associated with unfavorable functional outcomes. Furthermore, dementia was associated with increased 1-year death (HR = 1.98; 95% CI 1.60–2.48, <i>p</i> &lt; 0.001).</p> Conclusions <p>Preexisting cognitive impairment negatively influenced patient outcomes after stroke. The observed associations were independent of comorbid conditions, highlighting the importance of considering prestroke cognitive status in the design and interpretation of interventional studies aiming to improve stroke outcomes.</p>