Background: Low-level physical activity (PA) among Chronic Low Back Pain (cLBP) is associated with various biopsychosocial factors, and PA is effective in the domains of quality of life (QoL). Objectives: This research aimed to study the predictors of physical activity behavior among cLBP patients referred to comprehensive health service centers in the Shahid Beheshti University of Medical Sciences (SBUMS) in Tehran, Iran. Methods: In the present study 280 eligible patients with cLBP who referred to comprehensive health service centers in the SBUMS in Tehran, Iran from 13 January to 11 March 2019 were random selected. To diagnose the predictors of PA behavior, all the Theory of Reasoned Action (TRA) constructs were examined as risk factors to see if they influence on the probability of PA behavior occurrence and were interpreted through odds ratio (OR). SPSS version 21 was used to analyze the data. Results: Totally 280 cLBP patients with mean age of 57.07 ±13.09 years old participated in the study. This study showed that intention was significant predictor for perform the PA behavior OR (%95CI): 1.431(1.148-1.714), p-value <0.001), behavior beliefs could predictor for attitude OR (%95CI): 1.276(1.112-1.427), p-value= <0.001). attitude, normative beliefs, subjective norm ,and evaluation outcome behavior could predictors the cLBP patients for intention to perform the PA behavior OR (%95CI): 1.189(1.033-1.367), p-value=0.016)., OR (%95CI): 1.158(1.08-2.208), p-value<0.001) ., OR (%95CI):1.104(1.08-1.128), p-value=0.003) ., OR (%95CI): 0.814(0.74-1.554), p-value<0.001), but motivation to comply could predict the cLBP patients for subjective norm OR (%95CI): 1.077(0.891-1.263), p-value=0.093). Conclusion: This study showed that the cLBP patients who were normative beliefs and evaluation regarding PA behavior could effect on the intention to engage in greater PA than those with other constructs.