Background: Most of the previous researches on the abnormality of breathing pattern have focused on the silence of functional movements owing to such abnormality, however, have not been clearly identified the relationship between the abnormal breathing pattern on one hand and kinesiophobia and flexion relaxation phenomenon (FRP) on the other hand. Objective: To compare patients with chronic low back pain (CLBP) and healthy person in the abnormality of breathing pattern, kinesiophobia, and FRP during flexion and extension of the trunk. Design: Case-control study. Methods: The research subjects consisted of a group of 15 healthy adults and another group of 15 patients with CLBP. Capnography was used to measure the endtidal CO2 (EtCO2) and respiratory quotient (RQ). The muscle activity of multifidus and erector spinae of the subjects was measured during flexion and extension of the trunk to identify their FRP. The Nijmegen Questionnaire (NQ) and Tampa Scale of Kinesiophobia (TSK) were utilized to measure their breathing patterns and kinesiophobia, respectively. The Kolmogorov-Smirnov (K-S) test was conducted in order to analyze the normal distribution of the measured data. Their general characteristics were identified by the descriptive statistics and the independent t-test was performed to identify the differences between the two groups in terms of abnormality of breathing pattern, kinesiophobia, and FRP. The level of significance was set at α=.05. Results: The patients with CLBP had significantly less EtCO2 and shorter breathing hold time (BHT) than normal healthy person (p<.05). The patient with CLBP also had significantly greater kinesiophobia than healthy person (p<.05), and had less FRP than the healthy person (p<.01). Conclusions: These results suggest that the CLBP had greater abnormality of breathing pattern and kinesiophobia with less FRP than healthy person.