Background: Obesity is associated with worse outcomes in endometrial cancer, but the underlying mechanisms are poorly understood. In other obesity-related cancers, white adipose tissue inflammation (WATi) is an independent predictor of shortened cancer-specific survival. We hypothesized that WATi occurs in patients with endometrial cancers and is a prognostic marker of shortened survival. Methods: We conducted a retrospective cohort study in which patients with stage III or IV grade 3 endometrioid (G3) or serous endometrial cancer were included. Eligible subjects had archived omental and/or peri-nodal adipose tissue available. WATi was detected by the presence of dead/dying adipocytes surrounded by CD68+ macrophages forming a crown-like structure (CLS). Clinicopathologic data were abstracted from medical records. For association with WATi, Wilcoxon rank sum test was used for continuous variables, Fisher’s exact test for categorical variables. Log rank test was used to assess the association of WATi and survival. Results: A total of 95 patients who underwent debulking surgery from 2001–2017 were included (median age, 67 years; range, 33-86 years). Of these, 51 (54%) had WATi. The presence of WATi was unaffected by race, tumor histology or stage. Patients with WATi had a higher median body mass index (BMI) than those without WATi (32.17 and 27.33 kg/m², respectively; P< 0.001) and were more likely to be obese (P = 0.01). Patients with the most severe WATi (n = 20) had shorter progression-free survival (PFS) and a trend suggesting shorter overall survival (OS) than those patients with less severe or no WATi (n = 75) (median PFS 15.8 vs 59.2 months, respectively, P = 0.001; median OS 33.9 vs 59.4 months, respectively, P = 0.059). Conclusions: Visceral adipose inflammation is prevalent in obese patients with advanced G3 and serous endometrial cancer. Severe inflammation was associated with significantly worse PFS.