Although fatigue is considered to be one of the major causes of distress among cancer patients, little is known about its association with other factors, such as demographic, medical, and psychosocial factors. A total of 455 ambulatory cancer patients completed the Profile of Mood States (POMS) scale, which includes a fatigue subscale. Other information was obtained in an interview. The results of a multiple regression analysis suggested that sex, education, employment status, the size of the household, the performance status, and depressive mood were associated with fatigue. Our findings reveal that the fatigue experienced by cancer patients may be determined by multiple factors, including demographic, physical, and psychological factors.