This study aimed to evaluate the effectiveness of a modified package of exercise therapy combined with relaxation on pain intensity, range of motion (ROM), anxiety, and quality of life (QoL) in office workers with chronic lower back pain. In this clinical trial, 72 office workers aged 20 to 50 years with chronic low back pain were randomized to one of four groups including; group 1, exercise therapy; group 2, psychotherapy (relaxation therapy); group 3, modified protocol (exercise therapy followed by relaxation therapy); group 4, control group (no intervention). Participants exercised 3 times weekly for 6 weeks for 40-45 min of exercise/relaxation. Pain intensity, ROM, anxiety, and QoL were evaluated at baseline, 6 weeks, and 12 weeks after the end of the intervention. Results showed significant decreases in pain intensity and anxiety in the three experimental groups compared to the control group. The three intervention groups indicated a significant decrease in pain intensity and anxiety after 6 and 12 weeks. ROM significantly improved in the exercise therapy and the modified protocol over time (after 6 and 12 weeks). A significant difference in QoL was found between the groups, with the greatest improvement found in the psychotherapy and modified protocol groups. This therapeutic package (including exercise movements and psychological interventions) was found to have a superior effect on pain intensity, ROM, anxiety, and QoL after 6 and 12 weeks compared to other interventions (only exercise and psychotherapy).