To analyze changes over time and the predictive value of baseline and changes of sedentary time (ST) and physical activity (PA) on pain, disease impact, and health-related quality of life (HRQoL) at 2-and 5-year follow-up in women with fibromyalgia.Methods: This is a longitudinal and exploratory study with three time points.A total of 427 women with fibromyalgia (51.4 ± 7.6 years) were followed after 2 (n = 172) and 5 years (n = 185). ST and PA (light and moderate-to-vigorous [MVPA]) were assessed using triaxial accelerometers. Pain, disease impact, and HRQoL were measured using: pressure pain threshold, the pain subscale of the revised fibromyalgia impact questionnaire (FIQR), the bodily pain subscale of the 36-item short-form health survey (SF-36), a visual analog scale (VAS), the FIQR, and the SF-36 physical and mental components.