Lung cancer is a leading cause of death due to malignancy worldwide. Diaphragmatic metastasis secondary to primary lung cancer is rare. In the literature, only a few cases have been described as the majority of cases of diaphragmatic metastasis which are secondary to gastrointestinal neoplasia. The authors report a rare case of diaphragmmatic metastasis from a primary adenocarcinoma of the lung in a 76-year-old female patient with no history of active or passive smoking with progressive worsening fatigue, asthenia, malaise, and unquantified weight loss with three months of evolution, associated with pleuritic chest pain and edema of the lower limbs for fifteen days previous to hospital admission. Chest X-ray showed elevation of the right hemi-diaphragm and thoracic-abdominal-pelvic computed tomography revealed a complex multilobuled mass with neoformative characteristics intersecting the diaphragm and invading the dome liver and the right lung region. Biopsy of the mass was performed whose histological examination was consistent with moderately differentiated adenocarcinoma. Immunohistochemical examination was positive for cytokeratin 7 and negative forcytokeratin 20, suggesting primary lung tumor. A positron emission tomography was performed without uptake in other locations. Diagnosis of adenocarcinoma with diaphragmatic metastasis was then admitted and the patient started chemotherapy with carboplatin and gemcitabine. The patient died six months after the diagnosis. The authors also present a brief theoretical discussion based on the current and scarce literature on this rare entity.