Background: The aim of this study is to evaluate the impact of lymphovascular space invasion (LVSI) on the risk of lymph node metastases and survival in endometrioid endometrial adenocarcinoma.Material and methods: As regard the study design, this is a cohort study based on prospectively recorded data. Patients with endometrioid endometrial adenocarcinoma registered in the Swedish Quality Registry for Gynecologic Cancer 2010-2017 with FIGO stages I-III and verified nodal status were identified (n = 1587). LVSI together with established risk factors, namely DNA ploidy, FIGO grade, myometrial invasion and age, were included in multivariable regression analyses with lymph node metastases as the dependent variable. Associations between the risk factors and overall and relative survival were included in multivariable models. Estimates of risk ratios (RR), hazard ratios (HR), excess mortality rate ratios (EMR), and 95% confidence intervals (95% CI) were calculated.Results: The presence of LVSI presented the strongest association with lymph node metastases (RR = 5.46, CI 3.69-8.07, p < .001) followed by deep myometrial invasion (RR = 1.64, CI 1.13-2.37). In the multivariable survival analyses, LVSI (EMR = 7.69, CI 2.03-29.10,) and non-diploidy (EMR = 3.23, CI 1.25-8.41) were associated with decreased relative survival. In sub-analyses including only patients with complete para-aortic and pelvic lymphadenectomy and negative lymph nodes (n = 404), only LVSI (HR = 2.50, CI 1.05-5.98) was associated with a worsened overall survival.Conclusion: This large nationwide study identified LVSI as the strongest independent risk factor for lymph node metastases and decreased survival in patients with endometrioid adenocarcinomas. Moreover, decreased overall survival was also seen in patients with LVSI-positive tumors and negative lymph nodes, indicating that hematogenous dissemination might also be important.