OBJECTIVE: To address the variability in prevalence estimates and inconsistencies in potential risk factors for post-stroke cognitive impairment (PSCI) using a standardised approach and individual participant data (IPD) from international cohorts in the STROKOG consortium. METHODS: We harmonised data from thirteen studies based in eight countries. Neuropsychological test scores 2 to 6 months after stroke or TIA and appropriate normative data were used to calculate standardised cognitive domain scores. Domain-specific impairment was based on percentile cut-offs from normative groups, and associations between domain scores and risk factors were examined using one-stage IPD meta-analysis. RESULTS: In a combined sample of 3,146 participants admitted to hospital for stroke (97%) or TIA (3%), 44% were impaired in global cognition and 30–35% in individual domains 2 to 6 months after the index event. Diabetes and a history of past stroke were strongly associated with poorer cognitive function after covariate adjustments; hypertension, smoking and atrial fibrillation had weaker domain-specific associations. While there were no significant differences in domain impairment among ethno-racial groups, some inter-ethnic differences were found in the effects of risk factors on cognition. CONCLUSIONS: This paper confirms the high prevalence of PSCI in diverse populations, highlights common risk factors, in particular diabetes, and points to ethno-racial differences which warrant attention in the development of prevention strategies.