Background: A pilot study of an 8-week mindfulness-based stress reduction (MBSR) program on a sample of low back pain patients was conducted in order to assess the feasibility and effectiveness of the intervention as well as changes in an EEG pattern called thalamocortical dysrhythmia which is associated with chronic pain. Patients and Methods: 22 patients with chronic low back pain participated in an MBSR program. Effect sizes were measured for psychological functioning, pain severity, and quality of life. Furthermore, 4 parameters of the EEG power spectral density were assessed. Results: Medium size effect sizes were found for health-related quality of life (EQ-5D, VAS, d = 0.43, p = 0.02; SF-12, psychological functioning, d = 0.50, p = 0.05), health-related life satisfaction (questions on life satisfaction d = 0.69, p = 0.01), depression (HADS, d = 0.48, p = 0.04, Brief Symptom Inventory d = 0.41, p = 0.04), and affective pain perception (pain perception scale d = 0.50, p = 0.04). The most relevant pain severity measurements improved in the range of d = 0.45-0.75 (p = 0.01-0.24). EEG analyses revealed no differences between the pre- and post-intervention. Conclusion: MBSR is a feasible intervention for patients with low back pain. They benefit from medium size effects which are comparable to similar behavioral interventions. Randomized controlled trials are needed in order to determine the specificity of these benefits.