This study was designed to evaluate the effects of early physical therapy intervention on treatment outcomes for workers with acute low back injuries. A total of 3867 cases were randomly selected from the database of a large occupational health care provider. Cases were assigned to either the early therapy intervention group or one of the two comparison groups on the basis of their delay to physical therapy. The treatment outcomes for the three groups were compared. The results showed that patients in the early therapy intervention had more favorable outcomes than the two comparison groups. Specifically, patients in the early intervention group had fewer physician visits, fewer restricted workdays, fewer days away from work, and shorter case duration. These results provide a strong indication for the effectiveness of early therapy intervention. The financial implications of the findings is discussed.