The assessment of health-related quality of life (HRQoL) as a patient-reported outcome provides information about the patients' general well-being as well as the effects of the disease and its treatment. This study aimed to investigate HRQoL using both generic and haemophilia-specific QoL instruments and to assess the clinical factors associated with HRQoL among haemophilia patients in Korea. In this cross-sectional, multicenter, observational study, moderate-to-severe haemophilia patients aged 8-64 years were recruited between November 2012 and September 2013. The EQ-5D Questionnaire, EQ Visual Analogue Scale, and Haemophilia-Specific QoL (Haemo-QoL) Questionnaire (Haemo-QoL for 8-16 years and Haemo-A-QoL for ≥17 years) were used to assess HRQoL. A total of 605 participants with a mean age of 29.32 ± 12.62 years were enrolled. The mean Haemo-QoL scores revealed significant differences by age group (children vs. adolescent vs. adult, 26.44 ± 11.3 vs. 28.88 ± 11.1 vs. 38.43 ± 17.7, respectively, p < 0.001). "Sports and leisure," "family planning," and "view" in adults and "perceived support," "friends," and "dealing" in children and adolescents were identified as the domains with the greatest HRQoL impairments. HRQoL was significantly impaired in patients with the following clinical factors: hepatitis, haemophilia-induced disability, bleeding experiences within the last 6 months, joint bleedings within the last 6 months, and haemophilic arthropathy. According to the multivariate regression analysis, HRQoL showed a negative association with the presence of haemophilia-induced disability (β = 0.222, p < 0.0001), bleeding experiences within the last 6 months (β = 0.098, p = 0.010), and haemophilic arthropathy (β = 0.212, p < 0.0001). HRQoL decreased in patients with older age and impaired clinical conditions among moderate-to-severe haemophilia patients in Korea. These study findings may provide significant insights into the adequate haemophilia management using patient-reported measurements.