Objectives Although the importance of stretching exercise for pain-relieving and patient education is well documented for chronic lumbago patients, it is uncertain how effective on-the-job training (OJT) is for female caregivers in nursing homes. In the present pilot trial based on multicenter randomization, we evaluated the intervention effect of a lecture and stretching exercise on caregivers in nursing homes. Methods Eighty-eight female caregivers (four nursing homes) volunteered to participate in this study, and they were separated into two groups randomly. For the intervention group, guidance by an orthopedist and an exercise instructor were provided as one OJT, and stretching exercises for only 6 min every day were recommended for low back pain prevention to the caregivers. Low back pain visual analogue scale (VAS), physical fitness, and mental and physical health were compared at baseline and immediately after the intervention. Results A total of 29 (33%) participants withdrew by 12 weeks. Regarding the reasons for withdrawal, 28 participants resigned, and one took a leave of absence due to exacerbation of lumbago. Adherence to the stretching exercises was 2.3 ± 1.3 (mean ± SD) times per week. No significant differences were seen for any outcome measurements. The high adherence group (33 times per week) did not show a change in the VAS, but the low adherence group (\3 times per week) and control group showed a tendency towards an increased score (p = 0.068). Conclusions Even with the conduct of one OJT, and exercises of only 6 min every day, the adherence of caregivers was low, and there appeared to be few effects of the OJT.