Background/aim: The aim of this study was to investigate and compare the effect of different physical therapy (PT) session numbers on pain, impairment. and quality of life in patients with chronic low back pain (LBP).Materials and methods: In this prospective, randomized-controlled, single-blind trial, a total of 60 patients with chronic LBP were divided into 2 groups with simple randomization within the scope of the study. A PT program of a total of 10 sessions was applied for patients in Group 10 (n = 30) and a total of 15 sessions for patients in Group 15 (n = 30). The main outcome measures were fingertip-to-floor distance (FFD), a visual analog scale (VAS), the modified Oswestry Disability Index (mODI), and the Nottingham Health Profile (NHP).Results: We found statistically significant differences in both groups between the before-treatment (BT) and after-treatment (AT) results in terms of all evaluation parameters. We detected significant differences between the 2 groups in terms of AT VAS, mODI, NHP Pain, and NHP Total; however, no significant differences were found in terms of FFD and the other NHP subdimension levels.Conclusion: We determined that 15 treatment sessions were more effective than 10 sessions on pain and disability in patients with chronic LBP.