Study Design: Randomized controlled trial with blind assessor. Background: Low back pain (LBP) is one of the most prevelant and costly musculoskeletal conditions in the United States (US) resulting in more global disability than any other condition. Most patients with acute LBP will improve over a short time, but many patients will proceed to chronicity resulting in a reduced quality of life and a high societal burden. The treatment of LBP has been studied extensively, yet the most effective treatment strategies remain to be elucidated. Objective: The purpose was to determine the short-term effectiveness of thoracic manipulation when compared to sham thoracic manipulation. Methods: Consecutive patients in a large health care ssytem with LBP were stratified based on symptom duration and randomly assigned to one of two groups. The intervention group received three visits of thoracic manipulation and core strengthening exercises. The control group received core strengthening and sham manipulative therapy. Both groups received education regarding LBP. Factorial repeated measures ANCOVA was completed for pain, disability, and fear-avoidance with duration of symptoms as the covariate. Mann Whitney-U test was used for GROC at follow up. Multiple regression was used to determine follow up scores, with duration of symptoms and baseline scores as covariates. Results: Ninety participants completed the study. The overall group-by-time interaction for the ANCOVA was not significant for MODQ, NPRS, FABQ. GROC was not significantly different between the groups. Disability, pain, FABQ-PA and FABQ-total were significantly reduced from initial to final; however, there was no significant difference between groups. Intervention group did significantly differ in the multiple regression when baseline scores were accounted for with manipulation having lower disability. Time and duration of symptoms were the primary factors in predicting outcomes of disability and pain. Conclusion: The current study did not show improved outcomes in individuals with LBP receiving the thoracic manipulation. Patient education regarding nature of pain and impact on activity remain crucial in the management of this disabling condition. This trial was prospectively registered.