Background Homeless persons are those who carry out their activities of daily living in city parks and other facilities. Little is known about homeless patients with lung cancer in Japan. Therefore, we characterized the clinical features and outcomes of homeless people in metropolitan Tokyo. Methods Between January 2014 and August 2018, 2068 homeless patients were admitted to the homeless patient care unit at Tokyo Saiseikai Central Hospital. Of these, 13 patients were treated for primary lung cancer. We retrospectively analyzed the patients' clinical characteristics, including their age, gender, treatment, and outcome, obtained from the hospital's electronic medical records. Results A total of 13 patients were treated for lung cancer. The median age was 66.2 (range, 51-77) years old. Twelve patients (92.3%) were smokers. All of the patients were men and had advanced lung cancer. Of these, four patients had adenocarcinoma, four had squamous carcinoma, and four had other histologies. Ten patients received chemotherapy, and 3 received chemoradiotherapy (carboplatin, n=8; cisplatin, n=2, immune check point inhibitor, n=2; other, n=1). Of the patients on first-line treatment, 58% discontinued treatment, with 71% doing so willfully. The median overall survival was 7.5 (1-44) months. During the study, nine patients died in the hospital, and four were lost to follow up. Conclusion It is difficult for homeless patients to continue chemotherapy, and they often quit therapy willfully. Therefore, it is necessary to develop an education and health insurance support system to ensure treatment continuity in a good social environment.