Chronic fatigue syndrome receives little attention in the medical curriculum. This study explores UK medical students’ knowledge of and attitudes towards chronic fatigue syndrome. Semi-structured interviews (average length 22 minutes) were conducted with 21 participants (7 females and 14 males) in years 3 (n = 4), 4 (n = 11) and 5 (n = 6) of their studies. Inductive thematic analysis taking a realist perspective produced three themes: limited knowledge, influences on attitudes and training needs. Students acquired their knowledge and attitudes largely from informal sources and expressed difficulty understanding chronic fatigue syndrome within a traditional biomedical framework. Incorporating teaching about chronic fatigue syndrome into the medical curriculum within the context of a biopsychosocial understanding of illness could encourage more positive attitudes towards chronic fatigue syndrome.