Physical activity plays an important role in the prognosis of chronic low back pain (LBP); however, whether physical activity predicts pain intensity and disability remains unknown. This study investigated whether objective and subjective physical activity measures predict pain intensity and disability levels 6months later in patients with chronic LBP. Patients with chronic LBP seeking care at 2 outpatient physiotherapy clinics were recruited. At baseline assessment, we collected anthropometric/sociodemographic data, duration of symptoms, pain intensity, disability, and physical activity (accelerometer and questionnaire). After 6months, we reassessed pain and disability. Multivariable regression analyses were performed to investigate the association of physical activity measures with pain and disability at follow-up. A total of 179 patients with chronic LBP were included. High occupational physical activity at baseline predicted disability at 6-month follow-up (B = 1.22; 95% confidence interval, 0.21 to 2.21) after controlling for age and baseline disability, meaning that for every 1-point increase in occupational physical activity, disability increased on average by 1.22 point. The remaining physical activity measures showed no association with pain intensity or disability at follow-up. Higher perceived levels of occupational physical activity predicted higher disability levels at 6-month follow-up in patients with chronic LBP.