Background— Atrial fibrillation (AF) frequently occurs in patients with chronic kidney disease (CKD). However, the long-term impact of development of AF on the risk of adverse renal outcomes in patients with CKD is unknown. In this study, we determined the association between incident AF and risk of end-stage renal disease (ESRD) among adults with CKD. Methods and Results— We studied adults with CKD (defined as estimated glomerular filtration rate eGFR <60 mL/min per 1.73 m ² by the Chronic Kidney Disease Epidemiology Collaboration equation) enrolled in Kaiser Permanente Northern California who were identified between 2002 and 2010 and who did not have previous ESRD or previously documented AF. Incident AF was identified by using primary hospital discharge diagnoses or 2 or more outpatient visits for AF. Incident ESRD was ascertained from a comprehensive health plan registry for dialysis and renal transplant. Among 206 229 adults with CKD, 16 463 developed incident AF. During a mean follow-up of 5.1±2.5 years, there were 345 cases of ESRD that occurred after development of incident AF (74 per 1000 person-years) in comparison with 6505 cases of ESRD during periods without AF (64 per 1000 person-years, P <0.001). After adjustment for potential confounders, incident AF was associated with a 67% increase in the rate of ESRD (hazard ratio, 1.67; 95% confidence interval, 1.46–1.91). Conclusions— Incident AF is independently associated with increased risk of developing ESRD in adults with CKD. Further study is needed to identify potentially modifiable pathways through which AF leads to a higher risk of progression to ESRD.