[Purpose] This study examined low back pain patients’ decrease in pain and improvement in functionality after performance of a lumbar stabilization exercise using an oral assistive device, which can replace a lumbar assistive device. [Subjects and Methods] The experimental group (n=12) conducted a stabilization exercise using an oral assistive device after conventional physical therapy. The control group (n=12) received conventional physical therapy. In order to objectively measure pain in this study, a visual analogue scale (VAS) was used. In order to evaluate the subjects’ functional aspects while living with low back pain, the Oswestry Disability Index (ODI) was used. [Results] There were statistically significant improvements in the comparison of the VAS and ODI of the experimental group and the control group. The experimental group’s VAS and ODI significantly improved after the intervention compared to the control group. [Conclusion] The stabilization exercise using the assistive device after conventional physical therapy in the rehabilitation of low back pain patients reduced subjects’ pain and increased their functional activities.