Background Many studies have been done on paravertebral–intramuscular ozone therapy in the management of chronic mechanical low back pain and found that it is effective in pain and function improvement, but none of the studies were done to assess the benefit of addition of paravertebral–intramuscular ozone therapy to the traditional physical therapy in the management of chronic low back pain. Patients and methods The study included 160 patients who were diagnosed with chronic mechanical low back pain, and they were divided into two groups: group I included 80 patients treated with paravertebral oxygen–ozone (O2O3), infrared lamp therapy, and exercises, and group II included 80 patients treated with infrared lamp therapy and exercises. They were assessed by pain intensity measures such as visual analog scale (VAS) and verbal rating scale (VRS) and functional status measures such as the disability questionnaire − Roland Morris Disability Questionnaire (RMQ) − and the Revised Oswestry Disability Index (ODI). Patients were assessed before treatment, at the end of the treatment (after 4 weeks), and at a follow-up of 24 weeks. Results Improvement was achieved in all patients of both groups at 1 month, with statistically highly significant differences between the patients of group I regarding VAS, VRS, RMQ, andODI scales (P<0.001).Wefoundhighly significant differences betweenthe patients of group II regarding RMQ and ODI scales (P<0.001) and statistically significant difference between patients of the same group as regarding VAS and VRS (P<0.05) at 6 months. Group I showed continuous improvement in all variables with highly statistically significant difference (P<0.001) when comparing these with the pretreatment variables at all time points, whereas improvement did not continue with group II at the end of the 24 weeks, as no statistically significant differences were found regarding all measures of outcome scales (P>0.05). Conclusion O2O3 paravertebral injections combined with physical therapy in patients with chronic mechanical low back pain can offer significantly longer improvement in pain management and functional status in these patients.