Pain self-efficacy and fear of movement have been proposed to explain how pain can lead to disability for patients with chronic low back pain. However the extent to which pain self-efficacy and fear of movement mediate the relationship between pain and disability over time has not been investigated. This study aimed to investigate whether pain self-efficacy and/or fear of movement mediate the relationship between pain intensity and disability in patients with recent onset chronic low back pain. In a two-wave longitudinal design, 184 chronic low back pain patients completed measures for pain intensity, disability, pain self-efficacy and fear of movement at baseline and 12 months after the onset of chronic low back pain. Regression analyses were used to test the mediational hypothesis. We found that, when measured at the same time, both pain self-efficacy and fear of movement beliefs partially mediated the effects of pain intensity on disability at the onset of chronic low back pain. However, in the longitudinal analyses, only improvements in self-efficacy beliefs partially mediated the relationship between changes in pain and changes in disability over a 12 months period. We found no support for the theory that fear of movement beliefs mediate this relationship. Therefore, we concluded that pain self-efficacy may be a more important variable than fear of movement beliefs in terms of understanding the relationship between pain and disability.