Background and purpose <p>Previous studies had inconsistent results and often lacked pre-stroke cognitive assessments, hindering differentiation between stroke-related decline and normal ageing. To address this, we aimed to explore cognitive and functional change trajectories before and after stroke across countries.</p> Methods <p>This international population-based cohort study analyzed data from four nationally representative longitudinal studies across 23 countries: CHARLS, ELSA, HRS, and SHARE. A two-level growth model was used to estimate post-stroke cognitive trajectories, compared with those of stroke-free individuals.</p> Results <p>69,013 participants from four longitudinal cohorts were included and 2,106 participants had their first-ever stroke. Compared with stroke-free participants, stroke patients had faster pre-stroke cognitive decline, with adjusted differences in annual decline ranging from −&#xa0;0.033 to −&#xa0;0.049 SD/y across cognitive domains. Stroke correlated with an acute global cognitive drop (pooled <i>β</i> = −&#xa0;0.319 [95% CI −&#xa0;0.467 to −&#xa0;0.276]) and accelerated subsequent decline (pooled <i>β</i> = −0.039 SD/y). Post-stroke declines in memory (−&#xa0;0.015 SD/y), orientation (−&#xa0;0.033 SD/y), and executive function (−&#xa0;0.004 SD/y) were observed. Recurrent stroke linked to worse post-stroke decline; exclusion of these cases reduced estimated acute and pre-stroke decline by 23.05% and 13.79%, respectively. In stroke-free individuals, vascular risk factors and social isolation correlated with steeper cognitive decline, consistent across European, North American and Asian cohorts.</p> Conclusions <p>Our findings demonstrate that stroke links to acute reduction and ongoing accelerated decline in cognitive/functional abilities, starting pre-stroke and continuing post-stroke. This underscores the need to include multidimensional outcome measures in stroke care and emphasizes prioritizing cognitive health in stroke prevention and post-stroke management.</p>