Invasive adenocarcinoma of the ileum is a rare tumor with an incidence of 0.59 per 1 million. Given its location in the distal portion of the small bowel, it is difficult to diagnose early and is often only discovered during surgery. This challenge leads to late diagnoses and poor prognosis. Surgical resection is the gold standard for treatment, with adjuvant therapy occasionally playing a supporting role. We present the case of a 62-year-old male with a complex past medical history, including non-small cell lung cancer with metastases to brain and treated with irradiation and left parietal craniotomy 13 years prior to presentation. Our patient presented to a community hospital complaining of abdominal pain. Findings on abdominal computerized tomography (CT) with intravenous (IV) contrast was consistent with a mechanical obstruction of the small bowel. The patient was admitted to the general medical floor for non-operative management. However, after three days of unsuccessful non-operative management, he was taken to the operating room for diagnostic laparoscopy. Surgery revealed an obstructing mass in the distal third of the ileum, which was excised and found to be invasive adenocarcinoma on histology. Adenocarcinoma of the ileum is very difficult to diagnose preoperatively. As a result, it often leads to delays in treatment and a poor prognosis in many patients, including ours. Because of its very low prevalence, a high index of suspicion is required to make an early diagnosis and obtain definitive treatment.