Chronic fatigue syndrome (CFS) and Myalgic Encephalomyelitis (ME) are debilitating conditions found globally. Yet, most studies on these illnesses include patients from the United States (U.S) and the United Kingdom (U.K.). The current study compares impairment levels of 124 patients living in Japan with 210 patients from the U.S. All patients are from tertiary-care settings that specialize in ME/CFS. The DePaul Symptom Questionnaire and Medical Outcomes Short-Form 36 were completed and used to assess the participants' symptoms and functional abilities. The U.S. sample showed more impairment in neurocognitive, gastrointestinal and post-exertional malaise symptoms when compared to the Japanese sample. Japanese women demonstrated significantly worse impairment in physical, role-physical, and mental health functioning than Japanese men. Interestingly, Japanese women reported similar functional impairment levels to both men and women in the U.S., despite being less likely to receive disability benefits. These findings may be due to national differences in disability status and gender parity.