Background: Acute symptomatic seizures (ASyS) increase the risk of epilepsy and mortality after a stroke. The impact of the timing and type of ASyS remains unclear. Methods: This multicenter cohort study included data from nine centers between 2002 and 2018, with final analysis in February 2024. The study included 4,552 adults (2,005 female; median age 73 years) with ischemic stroke and no seizure history. We examined ASyS occurring within seven days after stroke. Main outcomes were all-cause mortality and epilepsy. Validation in three separate cohorts included 74 adults with ASyS. Results: The ten-year risk of post-stroke epilepsy ranged from 41% to 94%, and mortality from 36% to 100%, depending on ASyS type and timing. ASyS on stroke onset day had a higher epilepsy risk (aHR 2.3, 95% CI 1.3-4.0, p=0.003) compared to later ASyS. Status epilepticus had the highest epilepsy risk (aHR 9.6, 95% CI 3.5-26.7, p<0.001), followed by focal to bilateral tonic-clonic seizures (aHR 3.4, 95% CI 1.9-6.3, p<0.001). Mortality was higher in those with ASyS presenting as focal to bilateral tonic-clonic seizures on day 0 (aHR 2.8, 95% CI 1.4-5.6, p=0.004) and status epilepticus (aHR 14.2, 95% CI 3.5-58.8, p<0.001). The novel SeLECT-ASyS model, available as an app, outperformed a previous model in the derivation cohort (concordance statistic 0.68 vs. 0.58, p=0.02) and in the validation cohort (0.70 vs. 0.50, p=0.18). Conclusions: ASyS timing and type significantly affect epilepsy and mortality risk after stroke, improving epilepsy prediction and guiding patient counseling.