Objective: Primary Fallopian Tube Carcinomas (PFTCs) are gynecologic malignancies which mostly present abdominal symptoms or vaginal discharge. However, Malignant Pleural Effusion (MPE) as the initial and sole presentation of PFTC without abdominal symptoms and signs is very rare. Case report: We report a 68-year old female presented with MPE but her transvaginal ultrasound and Computed Tomography (CT) of abdominal and pelvic organs were negative for any suspicious tumor lesion. By combined immunohistochemistry of pleuracentesis, serum CA-125, and PET-CT narrows the diagnosis to a gynecologic origin. A final diagnosis of primary fallopian tube carcinoma originated from small foci of Serous Tubal Intraepithelial Carcinoma (STIC) was made by a laparoscopic surgery. By the literature review data, this is the second reported clinically occult primary fallopian tube carcinoma presenting only with malignant pleural effusion. Conclusion: PFTCs initially presenting as MPE are difficult to diagnose preoperatively. By combined immunohistochemistry of thoracentesis, tumor marker, and image study narrows the diagnosis to a gynecologic origin. Timeline of precancerous lesion (p53signature, STIC) to high-grade serous carcinoma and transmission routes of MPE were also discussed and presented in this report.