Background: Blood pressure (BP) extremes and renal (dys)function contribute to poor outcomes in patients with atrial fibrillation (AF). Using data from the prospective AF-GEN-UK study, we investigated the effect of systolic BP and interaction with renal function for prognostication. Methods: Baseline systolic BP (SBP) values were recorded for 1580 patients (mean [SD] age 71 [11] years, 60% male) and categorized as follows: 120–129 mmHg (n = 289, reference group) <110 mmHg (n = 165), 110–119 mmHg, (n = 254), 130–139 mmHg (n = 321), 140–159 mmHg (n = 385) and ≥160 mmHg (n = 166). Cox regression analysis, adjusted for age, oral anticoagulation (OAC) and CHA2DS2-VASc score established the impact of SBP, renal function and their interaction on 1-year outcomes. SBP groups were compared using ANOVA and chi-square tests. Results: OAC use was 84% and similar across SBP groups. Renal dysfunction [estimated baseline glomerular filtration rate (eGFR) < 60 ml/min] was present in 24%, with significantly lower eGFR values in the SBP 110–119 mmHg group. History of heart failure was significantly higher in those with SBP <110 mmHg. SBP <110 mmHg was predictive of all cause-death on univariate [hazard ratio (HR) 2.36, 95% confidence interval (CI) 1.20–4.64] and adjusted (aHR 9.71, 95% CI 1.73–54.5) regression. There was no statistically significant interaction between SBP and eGFR, no associations of SBP with haemorrhagic or thromboembolic events. Conclusions: In people with AF, SBP <110 mmHg was independently predictive of all-cause death, with no significant interaction between SBP and renal (dys)function. This may reflect general poor health and/or excessive antihypertensive therapy, which should be avoided.