Medical treatment for stroke prevention in cryptogenic stroke (CS) patients with patent foramen ovale (PFO) remains inconclusive. We compared the efficacy and safety of dabigatran with aspirin on stroke prevention for patients with recent CS and PFO.In this prospective cohort study, we randomly assigned patients with PFO who had a cryptogenic stroke, in a 1:1 ratio, to dabigatran or aspirin group. Patients were followed for 2 years and the primary efficacy outcome was the recurrence of stroke or systemic embolism. The primary safety outcome was occurrence of bleeding complications.A total of 375 patients were enrolled in the study, 188 assigned to the dabigatran group and 187 to the aspirin group. During the 2-year follow-up, the primary efficacy outcomes occurred in 4 patients in the dabigatran group (annualized rate, 2.0%) and 11 patients in the aspirin group (annualized rate, 5.1%) (hazard ratio, 0.74; 95% confidence interval, 0.51-0.98; P = 0.049). TIA/acute ischemic stroke occurred in 3 patients in the dabigatran group and 8 patients in the aspirin group (hazard ratio, 0.72; 95% confidence interval, 0.52-0.95; P = 0.039). Bleeding complications occurred in 8 patients in the dabigatran group (annualized rate, 3.9%) and in 7 patients in the aspirin group (annualized rate, 3.5%) (hazard ratio, 1.24; 95% confidence interval, 1.01-1.52; P = 0.886).For cryptogenic stroke with PFO, dabigatran was superior to aspirin for stroke prevention. There is no increased risk of bleeding complication with dabigatran.Copyright © 2022 Elsevier B.V. All rights reserved.