Objective: To assess the effect of different dosages of pain neuroscience education (PNE) programs on central nociceptive processing in patients with fibromyalgia. Second, to compare the effects of different dosages of PNE programs on numerical pain rating scale (NPRS), disability, and psychological variables. Design: Single-blind randomized controlled trial. Setting: Three fibromyalgia centers in Spain (Valencia, Alcorcón, Alcalá de Henares). Subjects: Seventy-seven patients with fibromyalgia. Methods: Participants were randomized to four groups of PNE: 1) high-dose PNE (N = 20), 2) low-concentrated dose PNE (N = 20), 3) diluted low-dose PNE (N = 20), and (4) control treatment (N = 17), conducted in two 30-50-minute sessions in groups of four to six participants. Conditioned pain modulation (CPM), temporal summation (TS), and pressure pain thresholds (PPTs) were assessed at baseline and at three-month follow-up. Secondary outcome measures were the Fibromyalgia Impact Questionnaire, Pain Catastrophizing Scale, and Pain Anxiety Symptoms Scale. Results: There were significant between-group differences for NPRS in favor of the groups receiving high-dose PNE, with a large effect size at three-month follow-up (P < 0.01, η2p = 0.170), but there were no significant differences between groups for the remaining variables (P > 0.05). All groups improved for central nociceptive processing, psychological variables, disability, and pain intensity (NPRS). Conclusions: In patients with fibromyalgia, higher dosages of PNE produced a larger improvement in pain severity at three-month follow-up than other dosages of PNE and biomedical education. However, PNE was not superior to biomedical education in the central nociceptive processing, disability, or psychological variables in patients with fibromyalgia.