Objective: To evaluate the effectiveness of Plai oil for treating myofascial pain syndrome.Material and Methods: One hundred and fourteen volunteers with muscle pain from myofascial pain syndrome participated in the study and had Plai oil, placebo oil and diclofenac gel applied to their shoulder and neck for 6 days. Clinical evaluation was determined using visual analogue scales, pressure threshold and cervical range of motion of neck flexion and neck extension measurements.Results: The results showed that the visual analogue scales of the 3 groups were significantly different from the baseline. The pressure threshold also increased significantly from the baseline (3.87±1.36) in the volunteers who applied Plai oil (4.42±1.34) and those who applied diclofenac gel (4.35±1.06). However, the results of treatment and placebo groups at the last follow-up were not significantly different. Interestingly, it was observed that Plai oil and placebo oil significantly increased the angle of neck flexion and extension within 3 days of application. Muscle pain treatment with Plai oil resulted in a good outcome that was no different to the outcome of applying the diclofenac gel and placebo.Conclusion: It was demonstrated that Plai oil is as effective for relieving myofascial pain as 1.0% diclofenac gel.The interpreted results of muscle pain are not fully clarified due to placebo effect and other influencing parameters. However, Plai oil also decreased muscle tension and improved the restricted range of motion. We can recommend that Plai oil can be used as an alternative topical application for muscle pain treatment.