Abstract: Fever occurs frequently in cancer patients, thus, it is very important to determine the etiology of fever in cancer patients. Neoplastic fever (NF) is a paraneoplastic syndrome caused by cancer itself, although the pathophysiology of NF remains uncertain. Research aimed at elucidating the mechanisms involved suggests the possible role of inflammatory cytokines that are released by cancer cells. Other mechanisms include tumor necrosis, which may be associated with the release of pyrogens from dead tissue. NF is a diagnosis of exclusion, that is, it can be suspected only after excluding identifiable etiologies. The naproxen test can be used to aid in the differentiation of NF from non-neoplastic fever. Once the diagnosis is established, disease-specific palliative chemotherapy and surgery may control NF, wherein naproxen and other anti-inflammatory agents can be effective for symptom palliation. The efficacy of the treatment was from 82% to 90%. However, if naproxen is used, the potential benefit of symptomatic palliation should be weighed against possible side effects like gastritis and gastrointestinal bleeding, as well as additional relative contraindications, such as cardiac, renal, and hepatic dysfunction.