Health-related quality of life (HRQOL) is an important goal of therapy for chronic myeloid leukemia (CML) patients treated with current molecular-targeted therapies. The main objective of this study was to investigate factors associated with long-term HRQOL outcomes of CML patients receiving imatinib. Analysis was performed on 422 CML patients recruited in an observational multicenter study. HRQOL was assessed with the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). Key socio-demographic and clinical data were investigated for their association with HRQOL outcomes. Chronic fatigue and social support were also investigated. Univariate and multivariate linear regression analyses were used to identify independent factors associated with HRQOL outcomes. Fatigue was the only variable showing an independent and consistent association across all physical and mental HRQOL outcomes (P<0.01). Differences between patients reporting low versus high fatigue levels were more than eight and seven times the magnitude of a clinically meaningful difference, respectively, for the role physical (Δ=70 points) and emotional scale (Δ=63 points) of the SF-36. Fatigue did not occur as an isolated symptom and was most highly correlated with musculoskeletal pain (r=0.511; P≤0.001) and muscular cramps (r=0.448; P≤0.001). Chronic fatigue is the major factor limiting HRQOL of CML patients receiving imatinib.