To investigate the association between L1 cell adhesion molecule (L1CAM) expression and lymph node (LN) metastasis in diabetic patients with endometrial cancer (EC). A matched case control study was conducted with each 34 diabetic and non-diabetic EC patients. L1CAM expression was evaluated by immunohistochemistry and its correlation with LN metastasis was examined. Of the 68 patients, 13 (19.1%) were positive for L1CAM immunostaining: 6 (8.8%) in tumor cells and 7 (10.3%) in tumor stroma. Positive rate of L1CAM expression in diabetic EC patients was similar to that in non-diabetic EC patients, irrespective of the area of L1CAM expression (14.7% vs. 23.5%, p=.355). Of 64 who underwent lymphadenectomy, 8 (12.5%) had LN metastasis: 4 diabetic and 4 non-diabetic EC patients. At 50.5 months of the mean follow-up (range 2-113 months), a total of three recurrences: 2 diabetic and 1 non-diabetic patients. Tumor recurred more in the patients with positive L1CAM expression in tumor cells than those with negative L1CAM expression for all enrolled patients (33.3% vs. 1.6%, p=.019). However, we failed to find any significant association between L1CAM expression and LN metastasis for the entire subjects. Only for the diabetic EC patients (n = 34), patients with pelvic LN metastasis showed L1CAM expression in tumor cells more than those without LN metastasis (50.0% vs. 3.6%, p=.035). Nevertheless, there was no significant association between paraaortic LN metastasis and L1CAM expression in tumor cells as well as in tumor stroma (p>.05 for both). Advanced stage was the only risk factor for recurrence that showed a significant association with L1CAM expression in tumor cells, but not in tumor stroma, of EC patients (p=.014). Moreover, in a subgroup analysis with the diabetic EC patients, the significant relationship between advanced stage and L1CAM expression in tumor cells was also observed (p=.006). L1CAM expression is associated with pelvic LN metastasis and advanced stage in diabetic patients with EC.