We report a case of non-acquired immunodeficiency syndrome-defining lung adenocarcinoma in a multidrug-resistant human immunodeficiency virus (HIV)-positive patient. The patient was a 47-year-old Japanese woman who received salvage combination anti-retroviral therapy with darunavir plus ritonavir plus raltegravir plus tenofovir/emtricitabine in May 2009. She was diagnosed with lung adenocarcinoma (T3N3M1, stage IV) in November 2010 and was not found to possess any activating mutations in the epidermal growth factor receptor gene. Therefore, 6 courses of carboplatin plus pemetrexed and 3 courses of gemcitabine followed by erlotinib were administrated, and therapy was changed to home medical care. The only drug-related adverse event was grade 1 neutropenia, and drug interaction between the simultaneously administered anti-retroviral and chemotherapeutic agents was not confirmed. The patient battled lung adenocarcinoma for 1 year after the diagnosis and died of cancer progression in October 2011. Her performance status was stable and the CD4 (+) lymphocyte count and HIV load were well controlled throughout the course of treatment. In conclusion, the agents used for this patient show high tolerability and can be used as an effective treatment strategy for lung cancer occurring in HIV-positive patients.