OBJECTIVE: The aim of this study was to evaluate the conditioned pain modulation of patients with fibromyalgia and compare it to that of healthy individuals before and after 3 months of strength training. METHODS: This is a prospective experimental study consisting of two independent, non-randomized groups: fibromyalgia (n=10) and healthy control (n=10). The research was conducted in person at the Unidade Saúde Escola of the Federal University of São Carlos, Brazil, during the period of June 2023-June 2024. The conditioned pain modulation test was administered to all patients in both groups. Twice a week (for 3 months), patients with fibromyalgia performed three sets of each exercise, with 10 repetitions, 40 s of muscle tension, and a 60-s interval between the sets. Subsequently, we compared the conditioned pain modulation test using the Student's t-test. RESULTS: Significant between-groups differences (p≤0.05) and large effect sizes (d≥0.8) that were observed at baseline (at times 2, 3, and 4) were not observed after 3 months of strength training, indicating that the intervention was able to improve the conditioned pain modulation in patients with fibromyalgia. Although the within-group comparisons (pre- and posttreatment) showed an absolute difference of 6.35 in central sensitization, this was not statistically significant (p≥0.05) and had a small effect size (d=0.27). CONCLUSIONS: The conditioned pain modulation of fibromyalgia patients appears to become similar to that of healthy individuals after 3 months of strength training.