The aim of the study was to determine the association of sex and race/ethnicity with acute hospital readmissions ("within-stay readmissions") during inpatient rehabilitation facility care versus patients discharged home without a within-stay readmission among traumatic brain injury patients. The study used a secondary analysis ( N = 210,440) of Uniform Data System for Medical Rehabilitation data using multiple logistic regression. Within-stay readmissions occurred for 11.79% of female and 11.77% of male traumatic brain injury patients. Sex-specific models identified insurance, comorbidities, and complications factored differently in likelihood of within-stay readmissions among female than male patients but association of all other factors were similar per group. Within-stay readmissions differences were more pronounced by race/ethnicity: White, 11.63%; Black, 11.32%; Hispanic/Latino, 9.78%; and other, 10.61%. Descriptive bivariate analysis identified racial/ethnic patients with within-stay readmissions had greater days from traumatic brain injury to inpatient rehabilitation facility admission (White, 17.66; Black, 21.70; Hispanic/Latino, 23.81; other, 20.66) and lower admission cognitive and motor function. Factors differed across models predicting within-stay readmissions for race/ethnic groups; age, admission motor and cognitive function, complications, and length of stay were consistent across groups. This study demonstrates disparities by race/ethnicity for inpatient rehabilitation facility within-stay readmissions among traumatic brain injury patients and factors predictive of this potentially preventable outcome by sex and race/ethnicity. Findings could inform care planning and quality improvement efforts for TBI patients.