Background: The prognostic implications of new-onset atrial fibrillation (AF) in conjunction with transcatheter aortic valve replacement (TAVR) is sparsely examined. Therefore, we aimed to examine the impact of first-time detected AF after TAVR on all-cause mortality and heart failure (HF). Methods: With Danish nationwide data from 2008 to 2021, we identified all patients who underwent TAVR and were alive 30 days after discharge (index date). Patients were categorized into i) no AF; ii) history of AF; and iii) first-time detected AF within 30 days after discharge. From the index date, two-year rates of all-cause mortality and HF admissions were compared using multivariable adjusted Cox analysis. Results: We identified 6,807 patients surviving 30 days beyond TAVR: 4,229 (62.1%) without AF (55% male, median age 81), 2,283 (33.6%) with history of AF (58% male, median age 82), and 291 (4.3%) with first-time detected AF (56% male, median age 81). Compared with patients without AF, adjusted analysis yielded increased associated hazard ratio (HR) of all-cause mortality in patients with history of AF (1.53 [95% confidence interval [CI], 1.32–1.77]) and in patients with first-time detected AF (2.06 (95%CI, 1.55–2.73]). Further, we observed increased associated HRs of HF admissions in patients with history of AF (1.70 [95%CI, 1.45–1.99]) and in patients with first-time detected AF (1.77 [95%CI, 1.25–2.50]). Conclusion: In TAVR patients surviving 30 days beyond discharge, first-time detected AF appeared to be at least as strongly associated with two-year rates of all-cause mortality and HF admissions, as compared with patients with history of AF.