To evaluate the effect of Amplatz sheath size used in percutaneous nephrolithotomy (PCNL) on postoperative outcomes, bleeding and renal impairment rates. We retrospectively evaluated the records of 91 patients who had undergone PCNL. We divided the patients into 2 groups according to Amplatz sheath size (22 and 30 French [F]) used in the PCNL procedure. Groups were retrospectively compared in terms of pre- and postoperative hemoglobin and renal function, mean nephrostomy time, mean nephrostomy tube diameter, mean operative time, mean hospitalization time and mean scopy time. Mean operative time, mean preoperative hemoglobin and serum creatinine values were similar in 2 groups. The mean stone diameter of patients in group 1 (22F) and group 2 (30F) were 38.47 ± 11.51 mm and 37.69 ± 12.33 mm, respectively. Pre- and postoperative hemoglobin (Hb) levels were 14.52 ± 1.5 g/dL and 13.51 ± 1.4 g/dL, respectively in group 1. Pre- and postoperative Hb level were 14.23 ± 1.6 g/dL and 10.73 ± 1.7 g/dL, respectively in group 2. There was a significant difference between the two groups in terms of mean scopy time (P = .023), postoperative Hb (P = .027), postoperative creatinine (P = .032), mean nephrostomy duration (P = .019), mean nephrostomy diameter (P = .028) and hospitalization time (P = .034). There was significant difference between the two groups in bleeding requiring blood transfusion (P = .023) and residual stone (P = .035). The smaller the Amplatz sheath used in PCNL, the lower kidney hemorrhage and renal function impairment happens.