Background: Seromucinous tumors, a category of ovarian epithelial tumors, were first described in the 2014 World Health Organization’s (WHO) classification of tumors of the female reproductive organs. However, seromucinous carcinoma was reviewed and removed from the fifth edition of the WHO classification in 2020. We aimed to report our experience with 11 seromucinous ovarian tumors (borderline tumors and carcinomas). Methods: The clinical and pathological features of 11 seromucinous ovarian tumors were examined. In addition, the pathological records of seromucinous carcinoma were re-examined by a pathologist to determine if they could be considered as a new classification. Results: Patient age ranged from 28 to 71 years, with a median age of 45.6 years. The median tumor markers levels were 2.0 ng/mL, 68.0 U/mL, and 36.6 U/mL for CEA, CA 19-9, and CA125, respectively. Pathological findings showed that endometriosis was present in five cases (four seromucinous borderline tumors and one seromucinous carcinoma). Most borderline tumors were diagnosed at an early stage; three were diagnosed with the International Federation of Gynecology and Obstetrics (FIGO) stage IA, three with stage ⅠC1, and one with stage IC2. Two cases of seromucinous carcinoma were diagnosed with FIGO stage IA and two were diagnosed with stage ⅠC2. There were two cases of recurrence; one was a seromucinous borderline tumor and one was a seromucinous carcinoma. All cases were classified as endometrioid carcinoma with mucinous differentiation. Conclusions: Our findings indicated the low reproducibility of seromucinous carcinoma diagnosis. As seromucinous tumors are relatively rare and the literature on them is limited, further studies on this topic are warranted.