BACKGROUND: Approximately 50% of strokes in patients with cancer are classified as cryptogenic after standard evaluation. Atrial cardiopathy could explain some cancer-related cryptogenic strokes. However, the relationship between cancer and atrial cardiopathy is uncertain. METHODS AND RESULTS: β CONCLUSIONS: In a multicenter, prospective, cryptogenic stroke cohort, history of cancer was not associated with selected biomarkers for atrial cardiopathy. REGISTRATION: URL: https://www.ClinicalTrials.gov; Unique Identifier: NCT03192215.