PURPOSE: Little is known about the impact of decreased walking capacity on clinical outcomes in elderly patients with cancer. This prospective observational study aimed to investigate the impact of walking capacity on the risk of disability and hospitalization in elderly patients with advanced lung cancer. METHOD: This study prospectively enrolled 60 patients aged ≥ 70 years with advanced non-small-cell lung cancer (NSCLC) scheduled to receive first-line chemotherapy or radical radiotherapy between January 2013 and December 2014 (trial registration number: UMIN000009768). Patients were classified into the mobile or less mobile group based on the median incremental shuttle walking distance (ISWD) before initial treatment. Assessments included the Barthel index, disability-free survival time, mean cumulative lengths of hospital stay, and inpatient medical costs. RESULTS: The median ISWD was 290 m (interquartile range, 245-357.5 m). The mobile group (ISWD ≥ 290 m) had a longer disability-free survival time than the less mobile group (ISWD < 290 m, 24.6 months vs. 8.4 months, p < 0.05). During the first year from study entry, the mobile group had shorter cumulative lengths of hospital stay (41.3 vs. 72.9 days/person, p < 0.05) and lower inpatient medical costs (\1.9 vs. \2.9 million/person, p < 0.05) than the less mobile group. CONCLUSION: Elderly NSCLC patients with adequate walking capacity showed lower risks of disability, shorter hospitalizations, and lower inpatient medical costs than patients with reduced walking capacity. Further prospective research is needed to validate these findings. The trial was registered with the University Hospital Medical Information Network as trial number UMIN000009768 on January 13, 2013. TRIAL REGISTRATION: UMIN000009768.