Background: Reactive atrial-based anti-tachycardia pacing (rATP) in CIED (cardiovascular implantable electronic devices) is effective in atrial fibrillation (AF) suppression. Uninterrupted systemic anticoagulation is recommended when this algorithm is activated to avoid stroke, however, the use of a rATP algorithm in patients with a left atrial appendage (LAA) closure device has not been studied. We assessed the safety and feasibility of rATP algorithm to sup‑ press AF in patients with a LAA closure device over an extended period. Methods: Data from 55 consecutive patients who underwent a ­Watchman® implant at a tertiary care hospital between September 1, 2015, and January 30, 2020, who also had an in situ ­Medtronic® CIED (45 with and 10 with‑ out rATP capability) were retrospectively reviewed. Results: The 55-patient cohort was 60% male, 77 ± 8 years old, ­CHA2DS2 -VASc score 5 (4–6), HAS-BLED score 3 (3–4), LVEF 53 ± 14%, LA size 4.4 ± 0.7 cm and ventricular pacing burden of 73 (1.4–98.3)%. The CIEDs (20 ICDs and 35 pace‑ makers) antedated ­Watchman® implants by 915 ± 725 days. Post-implant, all patients discontinued anticoagulation.Twenty patients in the rhythm-control group with active rATP algorithm displayed no increase in yearly AF burden and were less likely to develop permanent/long-standing persistent AF (p = 0.002) when compared to 35 patients in the rate-control group with CIEDs inactive/incapable of rATP over a ≤ 5-year follow-up. The longest AF episode in the rhythm-control group lasted 204 (19–2520) h. There was no increase in stroke/thromboembolism and a significant reduction in major bleeding noted over ≤ 5 years pre- versus post-implant in the whole cohort (p = 0.005). Conclusion rATP algorithm use is safe and feasible in patients with a ­Watchman® device. Patients should be fore‑ warned of a surge in post-Watchman® implant AF burden.