Fatigue is a common symptom in lung cancer patients undergoing chemotherapy. There has been little clinical attention paid to this issue, however. Most explorations of fatigue in lung cancer patients are cross-sectional studies, which cannot reveal long-term patterns of fatigue. The purpose of this study was to track the pattern of fatigue in lung cancer patients from initial diagnosis to one month after the completion of six cycles of chemotherapy at eight time points. The study adopted a longitudinal design. Thirty-one lung cancer patients were recruited to describe patterns of fatigue over time. The General Fatigue Scale was used to measure fatigue patterns. The results showed the long-term pattern of fatigue in lung cancer patients who underwent chemotherapy. The fatigue associated with chemotherapy peaked after treatment and remained elevated one week after each cycle of chemotherapy, and was observed to gradually diminish over time but never reached baseline values. These findings will help health care providers to understand fatigue patterns over time. They should also improve quality of care and fatigue management strategies for lung cancer patients undergoing chemotherapy.