OBJECTIVE: To investigate the effect of force applied during massage on relieving nonspecific low back pain (LBP). METHODS: This single-blinded, randomized controlled trial enrolled 56 female patients with nonspecific LBP at a single medical center. For each participant, the therapist performed a 30 min massage session (20 min general massage and 10 min focal massage) using a special instrument with a force sensor inserted, for a total of six sessions in 3 weeks. During the 10 min focal massage, HF and LF groups received high force (HF, ≥2 kg) and low force (LF, ≤1 kg) massage, respectively. The primary outcome was pain intensity (i.e., visual analog scale (VAS), 0-10), and secondary outcomes comprised pain pressure threshold, trunk mobility, LBP-associated disability, and quality of life. RESULTS: No significant between-group differences were observed in baseline characteristics. The HF group exhibited significantly lower VAS than did the LF group, with a mean difference of -1.33 points (95% CI: -2.17 to -0.5) at the end of the intervention, but no significant difference was noted at the end of the follow-up. A significant time effect ( CONCLUSIONS: Compared with LF massage, HF massage exerted superior effects on pain relief in female patients with nonspecific LBP at the end of intervention. Applying different levels of force showed no effects on LBP-associated disabilities and quality of life.