Background/aim: Hemodialysis patients face a high burden of cardiovascular diseases, which account for over 40% of mortality in this population. In these patients, approximately two-thirds of cardiovascular deaths are due to arrhythmia. The aim of this study was to determine whether the ultrafiltration rate is associated with morphological and functional parameters of the left heart and arrhythmias. Methods: This work was a cross-sectional observational clinical study, with 75 hemodialysis patients. Patients were divided into two groups based on ultrafiltration rate (UFR): higher-UFR group, ultrafiltration rate ≥ 10 mL/kg/h (n = 37); lower-UFR group, ultrafiltration rate < 10 mL/kg/h (n = 38). All patients were analyzed for myocardial morphological and functional parameters and arrhythmias. Results: Statistically significant higher values were observed for the left atrium diameter (LAD) (47.56 ± 4.82 vs. 44.75 ± 2.33 mm, p = 0.0019), the left atrial volume index (LAVI) (43.28 ± 7.13 vs. 36.43 ± 8.52 mL/m², p = 0.0003), and the left ventricular mass index (LVMI) (138.47 ± 29.32 vs. 116.04 ± 31.64 g/m², p = 0.0021) in the higher-UFR group. UFR was associated with LAD (OR: 3.6000, 95% CI: 1.3780–9.4053, p = 0.0089), LAVI (OR: 4.1067, 95% CI: 1.5478–10.8956, p = 0.0045), and LVMI (OR: 4.7619, 95% CI: 1.6825–13.4774, p = 0.0033). The frequency of ventricular and supraventricular arrhythmias was similar between the analyzed patient groups. Conclusions: Higher UFR was associated with structural changes in the left heart (LAVI, LAD, and LVMI), but not with other echocardiographic parameters or arrhythmias in hemodialysis patients.