BACKGROUND: The World Health Organization Disability Assessment Schedule (WHODAS) 2.0 is a generic instrument to assess disability. Pain and psychological factors seem to play a pronounced disabling role in fibromyalgia (FM). There are few studies that investigate the factors associated with disability in patients with fibromyalgia from the patient's perspective. Information about FM disability using self-reported questionnaires is limited. This study aimed to assess the relationship between the ordinal response variable (degree of disability), and four explanatory variables: pain intensity, depression, anxiety, and alexithymia. METHODS: One hundred fifteen women with FM were enrolled in the cross-sectional study. For the assessment of disability the WHODAS 2.0 (36-item version) was used. Univariate and multivariate (ordinal logistic regression) analyses were performed to assess the relationship between pain (Visual Analogue Scale), depression and anxiety (Hospital Anxiety and Depression Scale), alexithymia (Modified Toronto Alexithymia Scale) and disability. RESULTS: Disability was detected by global WHODAS score in 114 patients (99%), with the corresponding percentages for mild, moderate and severe disability being 11.3, 46.96 and 40.87%, respectively. Global WHODAS score was more severe among subjects with depression (50 vs 36.4, p < 0.001, effect size = 0.33) and alexithymia (50 vs 33.6, p < 0.001, effect size = 0.38). Pain intensity mean scores for mild, moderate and severe disability were 5.0, 6.1 and 7.3, respectively (p < 0.001, omega-squared = 0.12). Pain intensity explained the global disability degree and its domains except for the cognitive one. Whereas, depression explained cognitive and personal relation domains. On the other hand, alexithymia explained global disability degree and all domains of WHODAS 2.0 questionnaire. CONCLUSIONS: Most of the patients with fibromyalgia perceived themselves with moderate to severe disability. The main explanatory variables of the perceived disability were the pain intensity and psychological factors (alexithymia and depression).