BACKGROUND Serous tubal intraepithelial carcinoma (STIC) is proposed as the precursor of ovarian, tubal, and peritoneal high-grade serous carcinoma, but the clinical significance remains unclear, especially in the normal population. We report a rare case of STIC in a patient undergoing non-prophylactic surgery who developed PPSC without a strong family history or BRCA mutations. CASE REPORT A 62-year-old woman presented with an abnormal pap smear (ASC-H). She underwent vaginal wall biopsy, endocervical curettage, and HPV testing, which revealed vaginal wall intraepithelial neoplasia 3 and cervical intraepithelial neoplasia 3, HPV 68 positive. Laparoscopic total hysterectomy, including an upper vagina and bilateral salpingo-oophorectomy, was performed. Postoperative histopathologic examination revealed carcinoma in situ of the cervix, and, incidentally, a serous tubal intraepithelial carcinoma (STIC) in situ of both fallopian tubes. During follow-up, the patient was diagnosed with primary peritoneal serous carcinoma (PPSC), 22 months after the initial operation. BRCA mutations were not detected. The findings in our case, coupled with current evidence, suggest the distal fallopian tube as the source of PPSC. CONCLUSIONS After an incidental diagnosis of STIC, we recommend surveillance for BRCA mutations. Standard management remains unclear, but further surgical evaluation and/or chemotherapy should be considered in patients with isolated STIC.