INTRODUCTION: Hospital length of stay (HLOS) is a metric of injury severity, resource utilization, and healthcare access. Recent evidence has shown associations between Medicaid and increased HLOS after traumatic brain injury (TBI). Whether managed care organization (Medicaid-MCO) or fee-for-service (Medicaid-FFS) models affect HLOS is unknown. METHODS: The Department of Health Care Access and Information Patient Discharge Database years 2017-2019 were queried for TBI patients aged =18-years (y) using ICD-10 codes (S06.0-S06.9/A). Inclusion criteria were Medicaid-MCO/Medicaid-FFS or PI not designated as death/hospice within 5-days of hospitalization. Demographic, socioeconomic status (SES), care-related, charges, and HLOS variables were compared. Subgroup analyses were performed in severe TBI (intracranial pressure monitor/craniotomy = Yes). Multivariable negative binomial regressions assessed the relationship between insurance and HLOS, adjusting for demographic, SES, injury severity, diagnosis-related group, and major complication/comorbidity. Incidence rate ratios (IRR) were reported. RESULTS: Overall (N = 39,834), 33.2% were Medicaid-MCO, Medicaid-FFS = 24.2%, and PI = 42.6%. Significant differences (p < 0.001) were observed for age (MCO = median 45y, FFS = 37y, PI = 44y), sex (male: MCO = 70.8%, FFS = 80.1%, PI = 68.8%), race (Hispanic: MCO = 35.0%, FFS = 51.6%, PI = 24.6%), lowest-quintile SES (MCO = 33.1%, FFS = 31.9%, PI = 9.0%), discharge to home (MCO = 72.1%, FFS = 76.8%, PI = 68.5%), and charges (MCO = median $100,297, FFS = $120,062, PI = $91,863). HLOS was longest in FFS (median = 4-days [IQR: 2-11], MCO = 4-days [2-9], PI = 3-days [1-7]). These differences were conserved in severe TBI (N = 1,650; MCO = 32.8%, FFS = 31.8%, PI = 35.3%) at greater magnitudes (home discharge: MCO = 15.5%, FFS = 25.6%, PI = 8.2%; charges: MCO = $629,625, FFS = $724,225, PI = $607,082; HLOS: MCO = 22-days [IQR: 13-34], FFS = 26-days [14-44], PI = 17-days [10-27]). On multivariable regression, Medicaid-FFS and MCO had significantly longer HLOS compared with PI in all TBI (IRR = 1.44 [95% CI: 1.41-1.48], IRR = 1.17 [1.15-1.20], respectively) and severe TBI (IRR = 1.52 (1.40-1.65), IRR = 1.25 [1.15-1.36], respectively). CONCLUSIONS: Medicaid-FFS had the highest likelihood of increased HLOS. Medicaid-MCO appeared to be a distinct risk stratum with shorter HLOS and lower hospital charges than Medicaid-FFS. Reasons may include different efficacies in care delivery and reimbursement, and require further investigation.