BACKGROUND Medicaid insures an increasing proportion of adults in the United States. Physical therapy use for low back pain (LBP) in this population has not been described. OBJECTIVE The study objectives were: (1) to examine physical therapy use by Medicaid enrollees with new LBP consultations and (2) to evaluate associations with future health care use and LBP-related costs. METHODS The study was designed as a retrospective evaluation of claims data. METHODS A total of 2,289 patients with new LBP consultations were identified during 2012 (mean age=39.3 years [SD=11.9]; 68.2% women). The settings in which the patients entered care and comorbid conditions were identified. Data obtained at 1 year after entry were examined, and physical therapy use was categorized with regard to entry setting, early use (within 14 days of entry), or delayed use (>14 days after entry). The 1-year follow-up period was evaluated for use outcomes (imaging, injection, surgery, and emergency department visit) and LBP-related costs. Variables associated with physical therapy use and cost outcomes were evaluated with multivariate models. RESULTS Physical therapy was used by 457 patients (20.0%); 75 (3.3%) entered care in physical therapy, 89 (3.9%) received early physical therapy, and 298 (13.0%) received delayed physical therapy. Physical therapy was more common with chronic pain or obesity comorbidities and less likely with substance use disorders. Entering care in the emergency department decreased the likelihood of physical therapy. Entering care in physical medicine increased the likelihood. Relative to primary care entry, physical therapy entry was associated with lower 1-year costs. CONCLUSIONS A single state was studied. No patient-reported outcomes were included. CONCLUSIONS Physical therapy was used often by Medicaid enrollees with LBP. High rates of comorbidities were evident and associated with physical therapy use. Although few patients entered care in physical therapy, this pattern may be useful for managing costs.