Sentinel lymph node (SLN) mapping allows node-negative patients to be spared from the surgical comorbidities associated with total lymphadenectomy. This study aimed to evaluate the oncological outcomes of SLN biopsy versus complete lymph node dissection in patients with early-stage endometrial carcinoma. Retrospective analyses were performed in patients with pathologically confirmed endometrioid endometrial carcinoma, who underwent minimally invasive surgical staging with SLN biopsy or complete lymph node dissection at Yonsei Cancer Center between 2015 and 2019. A total of 301 patients were included in this study. Eighty-two patients underwent SLN biopsy, while 219 underwent complete lymph node dissection. There were no significant differences in patient characteristics between the two groups. In terms of operative characteristics, the SLN biopsy-only group had a significantly shorter surgical duration (p < 0.001) than the lymphadenectomy group. The mean follow-up period was 41.4 months. There were no differences in progression-free survival (PFS) and overall survival (OS) between the two groups (SLN biopsy vs. complete lymph node dissection; p = 0.798 and 0.301, respectively). Multivariate analysis revealed that SLN biopsy was not an independent prognostic factor for PFS or OS. Our results showed that SLN biopsy provided oncological outcomes similar to those of lymphadenectomy.