Introduction: The purpose of this study was to evaluate prognostic factors for patients with upper urinary tract urothelial carcinoma (UUT-UC) after nephroureterectomy and to seek a better way of finding more favorable clinical results for these patients. Patients and Methods: We retrospectively reviewed the medical records of 121 UUT-UC patients who underwent a nephroureterectomy at our institution, and analyzed the prognostic significance of various clinicopathological parameters for progression-free and disease-specific survival rates by using univariate and multivariate analysis. Results: A Cox proportional hazards model showed that extravesical tumor recurrence after surgery was an independent prognostic factor for disease-specific survival (p < 0.0001). An additional model showed that lymphovascular invasion (LVI) was one of the independent predictors of lower extravesical-recurrence-free survival rates (p = 0.0004). Our final finding was that pathological tumor stage and positive surgical margin were significantly associated with the presence of LVI (p < 0.0001 and p = 0.0029, respectively). Conclusions: We conclude that there is a high possibility of LVI in patients with large tumors. Our findings should be helpful in terms of determining whether or not to perform neoadjuvant chemotherapy for patients with large tumors, given the fact that we frequently find a severe reduction in renal function after nephroureterectomy.