We aimed to evaluate the long-term complications and predisposing factors for these complications in patients with malignant ureteral obstruction (MUO) treated with percutaneous nephrostomy (PN). The records of patients with MUO treated with PN between January 2015 and 2018 were retrospectively reviewed for PN dislodgement, PN obstruction, PN replacement, pyelonephritis, hospitalizations due to PN complications, and other complications due to PN such as macroscopic hematuria, skin infections, or renal/perirenal abscess. Data for a total of 147 patients (229 renal units [RU], 107 males, 40 females) were evaluated. In 174 (76%) RU, PN was replaced due to PN dislodgement. The predisposing factors for PN dislodgement were follow-up time, body mass index (BMI), chemotherapy, diabetes mellitus (DM), low educational level (LEL), pyelonephritis, and catheter-related skin infections (CSRI). The PN was replaced in 40 RU due to obstruction. The predisposing factors for obstruction were follow-up time and BMI. Pyelonephritis developed at least once in 61 (41.5%) patients. Follow-up time, BMI, previous surgery, DM, and LEL were the predisposing factors for pyelonephritis. CSRI developed in 16 RU. Follow-up time, BMI, DM, and LEL were the predisposing factors for CSRI. Macroscopic hematuria developed in 11 patients. Follow-up time, previous surgery, DM, chemotherapy, and LEL were predisposing factors for macroscopic hematuria. The most common complication in patients with MUO treated with PN was PN dislodgement. However, life-threatening complications such as macroscopic hematuria and severe infections can also occur. Patients with DM, LEL, and chemotherapy are at high risk of PN-related complications.