Background: Atrial fibrillation (AF) and chronic kidney disease (CKD) are known to increase the risk of stroke. Objectives: We set out to examine the risk of stroke by kidney function and albuminuria in patients with and without AF. Design: Retrospective cohort study. Settings: Ontario, Canada. Participants: A total of 736 666 individuals (>40 years) from 2002 to 2015. Measurements: New-onset AF, albumin-to-creatinine ratio (ACR), and an estimated glomerular filtration rate (eGFR). Methods: A total of 39 120 matched patients were examined for the risk of ischemic, hemorrhagic, or any stroke event, accounting for the competing risk of all-cause mortality. Interaction terms for combinations of ACR/eGFR and the outcome of stroke with and without AF were examined. Results: In a total of 4086 (5.2%) strokes (86% ischemic), the presence of AF was associated with a 2-fold higher risk for any stroke event and its subtypes of ischemic and hemorrhagic stroke. Across eGFR levels, the risk of stroke was 2-fold higher with the presence of AF except for low levels of eGFR (eGFR < 30 mL/min/1.73 m², hazard ratio [HR]: 1.38, 95% confidence interval [CI]: 0.99-1.92). Similarly across ACR levels, the risk of stroke was 2-fold higher except for high levels of albuminuria (ACR > 30 mg/g, HR: 1.61, 95% CI: 1.31-1.99). The adjusted risk of stroke with AF differed by combinations of ACR and eGFR categories (interaction P value = .04) compared with those without AF. Both stroke types were more common in patients with AF, and ischemic stroke rates differed significantly by eGFR and ACR categories. Limitations: Medication information was not included. Conclusions: Patients with CKD and AF are at a high risk of total, ischemic, and hemorrhagic strokes; the risk is highest with lower eGFR and higher ACR and differs based on eGFR and the degree of ACR.