Endometrial cancer is often directly related to obesity and interventions for weight loss have mixed results. Risk factors for continued weight gain after diagnosis are not clearly defined in the literature. The objective of this study is to describe risk factors associated with increased body mass index (BMI) trajectory among endometrial cancer patients. Patients who were surgically treated for endometrial cancer at a single institution between 2010 and 2015 were identified. Demographics including age, race/ethnicity and estimated median income at diagnosis were obtained. BMI at five time points after diagnosis were calculated. BMI trajectories were estimated by latent class growth modeling using the PROC TRAJ procedure in SAS. Chi-squared tests and ANOVA were used to assess differences between trajectory groups. Statistical significance was set to a p-value<0.05. Of 695 patients included in the study, the average age at diagnosis was 62years and over 70% of patients were obese at baseline. Patients experienced increasing, stable, or decreasing BMI over 2years following diagnosis. Patients with younger age and lower estimated median income were most likely to be in the increasing BMI group. Among obese patients, those with Class I obesity (BMI 30 to 34.9kg/m2) were most likely to experience decreasing BMI and those with Class III obesity (BMI>40kg/m2) were most likely to experience increasing BMI, p<0.0001. A third of endometrial cancer survivors experience increasing BMI. Severity of obesity at diagnosis matters, patients with severe obesity (Class III) were most likely to experience weight gain.