Abstract: Background: Lumbar functional instability (LFI) may be associated with chronic low back pain (CLBP). Various therapeutic exercises were proposed to enhance spinal stability, such as core stability exercises (CSE) and deep breathing training (DBT). However, no study has examined and compared the effectiveness of delivering these exercises as an online program on patients with CLBP and LFI. Purpose: To evaluate and compare the short-term effects of three online exercise programs (DBT, CSE, and combined DBT+CSE) in females with CLBP and LFI. Method: A quasi-experimental study involving seventy-eight women aged between 25-40 years old. Participants were allocated into one of the three online therapeutic exercise program groups or the wait-list control group. All therapeutic programs were performed three times a week for four weeks. The intensity of LBP [Numeric Pain Rating Scale (NPRS)], functional disability [Oswestry Disability Index (ODI)], and core muscle endurance [Prone Bridge Test (PBT)] were measured at the baseline, end of the second week, and end of the fourth week of intervention. Results: All outcome measurements showed improvements at the end of four weeks in all groups (NPRS: ≥ 3.3 points, P<0.001; ODI: ≥ 12.4%, P<0.001; PBT: ≥ 18.7 sec, P<0.001), except the control group (NPRS: 0.3 points, P=0.174; ODI: 0.9%, P=0.149; PBT: 1.1sec, P=0.079). However, there were no differences between the three online therapeutic groups in any outcome measure (P>0.05), except that the combined DBT+CSE group showed statistically better improvement than the DBT group in PBT (19.3sec, P=0.028). This difference between the DBT+CSE and DBT did not reach the minimal detectable change. Conclusion: The three online therapeutic exercise programs effectively reduced LBP intensity and improved functional status and core muscle endurance, with no program being superior to the others. Further investigation is required through comparing the same online exercise programs with the in-clinic exercise method. Keywords: Chronic low back pain, core stability exercises, deep breathing training, lumbar functional instability, online program.