Self-efficacy that is associated with various pain-related disabilities such as chronic low back pain (LBP), should be questioned besides physical assessments. To investigate the physical factors associated with self-efficacy in patients with chronic mechanic LBP. One hundred nine patients diagnosed as chronic mechanic LBP (65 females, 44 males) between 20-50 years old were included to this study. The intensity of LBP was assessed by using a 10-cm Visual Analogue Scale. For musculoskeletal fitness measurement; muscle strength, muscle endurance, and flexibility tests were applied. Functional Reach Test for balance evaluation, Self-Efficacy Scale for self-efficacy measurement, Roland-Morris Disability Questionnaire for disability level evaluation were used. We found a moderate negative correlation between self-efficacy and pain intensity (r=-0.506); a negative and strong correlation between self-efficacy and disability level (r=-0.654) (p< 0.05). Self efficacy had a significant association with right (r= 0.265) and left (r= 0.290) lateral side bending flexibility (p< 0.05). According to multiple regression analysis results, it was found that disability level had a significant effect on self-efficacy (β=-2.014; p< 0.01). Poor musculoskeletal fitness and pain intensity may cause decreasing self-efficacy but the major determinant of decreased self-efficacy was low-back related disability scores.