STUDY DESIGN: Prospective multi-center cohort study. OBJECTIVE: To evaluate the effect of pre- and postoperatively assessed fear avoidance beliefs (FAB) on pain and disability in patients with degenerative lumbar spinal stenosis (LSS) after decompression surgery. SUMMARY OF BACKGROUND DATA: To the present, the influence of pre- and postoperative FAB on the prognosis after surgery for LLS is still unclear. METHODS: Patients of the Swiss Lumbar Stenosis Outcome Study (LSOS) with confirmed LSS undergoing first-time decompression without fusion were enrolled in this study. The main outcome of this study was minimal clinically important difference (MCID) in SSM symptoms (pain) and function (disability) after twelve months. To analyze the influence of pre- and postoperatively assessed FAB on pain and disability we built simple and multiple logistic regression models. RESULTS: In this analysis of 234 patients undergoing decompression surgery for symptomatic degenerative LSS we found baseline FAB measured by the FAB physical activity subscale (FABQ-P) not to be associated with pain (OR 0.95; 95% CI: 0.55-1.67) and disability (OR 1.11; 95% CI: 0.64-1.92) at twelve months' follow-up. In the final multiple logistic regression models patients with high FABQ-P at six months (OR 0.46; 95% CI: 0.24-0.91) and high persistent FABQ-P at baseline and six months (OR 0.34, 95% CI: 0.16-0.73) were less likely to report a MCID for SSM symptoms at twelve months. Our analysis found a similar trend for disability, however, the results were not statistically significant. CONCLUSIONS: In elderly patients undergoing decompression surgery for symptomatic degenerative LSS preoperative fear avoidance beliefs were not a prognostic indicator for the outcome. Patients with FAB at six months and persistent FAB were less likely to experience clinically relevant improvement in pain at twelve months. Studies should address the importance of persistent postoperative FAB.