Left atrial (LA) volume index (LAVI) has been considered a stable indicator of diastolic dysfunction and an independent predictor of mortality in patients with end-stage renal disease. To date, however, little is known about the relationship between LA enlargement and the changes in residual renal function (RRF).This study was undertaken to investigate the association between LA enlargement and the decline in RRF in 121 incident peritoneal dialysis patients. Within 2 months after the initiation of peritoneal dialysis, LA enlargement was determined by echocardiography and RRF by 24-hour urine collection. Subsequently, RRF was measured every 6 months.The rates of decline in RRF were significantly greater in patients with LA enlargement (LAVI > 32 mL/m 2 ) compared with those without LA enlargement (−0.17 ± 0.18 vs −0.07 ± 0.16 mL/min/month/1.73 m 2 , P = .002). In a linear mixed model, there was a significant difference in the rates of RRF decline over time between patients with and without LA enlargement (P < .001). Pearson’s correlation analysis revealed that there were significant inverse correlations between the rates of the decline in RRF and LAVI (r = −0.22, P = .018). In multiple linear regression analysis adjusted for other risk factors, LAVI was found to be an independent determinant of the rates of decline in RRF (β = −0.026, P = .018).This study shows that a higher LAVI is independently associated with a more rapid decline in RRF in patients with end-stage renal disease on peritoneal dialysis.