Aim: This research is the first to evaluate the effectiveness of trans-vaginal photobiomodulation therapy (TV-PBMT) for chronic pelvic pain. Materials & methods: Observational analysis of 128 women, undergoing TV-PBMT for chronic pelvic pain. Minimal Clinically Important Difference, defined as ≥2-point drop on a 0–10 numeric pain rating scale (NPRS), and effect size Cohen d coefficient, was calculated over nine treatments for overall pain, and pain with activities. Results: Compared with baseline, 64.5% of women showed improvement in overall pain, pain with bowel movement, intercourse, exercise, urination, sitting and vulvar pain (Minimal Clinically Important Difference = -2.4, -2.0, -2.4, -2.1, -2.1, -2.0, -3.1; d = 0.9, 0.7, 0.9, 0.7, 0.7, 0.7, 0.9) by treatment 9. Conclusion: In this cohort, TV-PBMT resulted in improvement of pelvic pain without serious adverse events.