Objective: The aim of this study is to analyze the prognostic role of lymph-vascular space invasion (LVSI), evaluated in a semi-quantitative fashion on prognosis of early stage, low risk endometrial cancer (EC). Methods: We enrolled patients who underwent surgery for endometrial cancer between 2003 and 2018 in two referral cancer center. All patients had endometrioid EC, G1–G2, with myometrial invasion <50%, and no lymph-node involvement. LVSI was analyzed in a semi-quantitative way, according to a 3-tiered scoring system in absent, focal and substantial. Results: Among 524 patients, any positive LVSI was found in 57 patients (10.9%) with focal LVSI (n=35, 6.7%) and substantial LVSI (n=22, 4.2%). Substantial LVSI was associated to higher rate of G2 (p<0.001), myometrial infiltration (p=0.002) and greater tumor dimensions (p=0.014). Patients with substantial LVSI were more likely to receive adjuvant treatment (6.6% vs. 52.6%, p<0.001). The 5-year OS was 99.5% in patients with absent LVSI and 70.6% in those with substantial LVSI (p<0.001). The 5-year disease free survival (DFS) was 93.6% in patients with absent LVSI and 56.5% in those with substantial LVSI (p<0.001). The rate of distant failures increased from 1.8% for absent LVSI to 22.7% for substantial LVSI (p=0.002). In univariate analysis substantial LVSI was the strongest predictor of poor overall survival (hazard ratio [HR]=11.9, p=0.001). Multivariate analysis showed that substantial LVSI was an independent predictive factor of both recurrence (HR=5.88, p=0.001) and distant failure (HR=10.6, p=0.006). Conclusions: Substantial LVSI represents the strongest independent risk factor for decreased survival and distant relapse, indicating a role for potential hematogenous dissemination.