Objectives: The purpose of this study was firstly to introduce a Participatory Action-Oriented Training (PAOT) program for the prevention of work-related musculoskeletal diseases (WRMSDs) in Small and Medium sized Enterprises in the Gumi Industrial Zone, and secondly to assess its effect. Methods: Two PAOT workshops to prevent WRMSDs were conducted with 39 volunteer participants from 10 companies selected (on a first-come, first-served basis) among 200 small- or medium-sized enterprises in Gumi. These companies had been provided with mandatory occupational health management agency services for Small and Medium sized Enterprises by an occupational medicine clinic. Each workshop consisted of 6 technical sessions and one closing ceremony. At the 1st session, the principles of each action checklist item were explained and an on-site checklist exercise was carried out. The 2nd to 5th sessions presented good example pictures on 4 subjects: material storage and handling, working environment, work organization and work-related welfare. Group discussions were carried out by the participants. In the final 6th session on the implementation of improvement, each participant was asked to present 6 action plans, 3 short-term and 3 long-term, for their own workplace improvement. Results: Overall, the participants worked out 47 real action plans, 27 short-term and 20 long-term, for improvement of their own workplaces. Three to 6 months after the workshops, through in-person visits to each company, it was confirmed that more than half of these 47 plans had been completed; 25 plans (53.2%) had been completed as planned, 8 (17.0%) were in processing, and 14 (29.8%) had not yet been put into practice. Conclusions: The study findings confirmed that the PAOT program holds strong potential as an intervention method to prevent WRMSDs in Small and Medium sized Enterprises, although the final results have not been fully assessed yet.