The current case is about a 62-year-old female presented with persistent fever for 10 days and yellowing of the skin for 5 days at our outpatient clinic. Laboratory tests revealed elevated levels of total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and γ-glutamyl transpeptidase. Abdominal computed tomography, magnetic resonance imaging, and magnetic resonance cholangiopancreatography revealed a mass in the ampulla of Vater, as well as dilatation of the intra- and extra-hepatic bile and pancreatic ducts. The patient underwent pancreaticoduodenectomy under general anesthesia. Post-operative pathological and immunohistochemical results confirmed a tumor located in the ampulla, measuring 1.5 × 1 × 1 cm. The main component of the tumor was a moderately differentiated pancreaticobiliary adenocarcinoma (ADC), combined with squamous cell carcinoma (SCC) as well as small cell neuroendocrine carcinoma (SCNEC). The cancer tissue infiltrated the entire intestinal wall, with no invasion of microvessels, lymphatic vessels, or nerves observed. Until 46 months later, there was no tumor recurrence or distant metastasis. We present an uncommon case of ADC of the ampulla of Vater combined with SCC and SCNEC. Carcinoma of the ampulla of Vater may have mixed histological components; therefore, in cases of ampullary carcinoma, appropriate specimen collection is necessary, and further studies with more focus on histological origins are required.