Inpatient acute rehabilitation is crucial in the management of patients after injuries, surgery, or those with debilitating or neurological conditions. Orthostatic hypotension (OH) is commonly associated with these conditions and can negatively impact their recovery. We found an incidence of OH of 4% in a cohort of 8350 patients at Vanderbilt Stallworth Rehabilitation Hospital (60±17yr, 72% men vs. non-OH 60±18 yr, 57% men). On admission, OH patients had a longer predicted length of rehabilitation hospitalization stay (LOS; 18±6 vs. non-OH 16±5 days; P<0.01) and lower Functional Independence Measure (FIM, 49±19 vs. non-OH 55±19; P<0.01), reflecting greater medical complexity. Actual LOS was even longer than predicted in OH (actual-predicted LOS [ΔLOS], 1±11 vs. non-OH -2±8 days; P<0.01) and FIM efficiency was lower ([discharge-admission FIM]/LOS, 2.5±1.6 vs. non-OH 3.1±1.9; P<0.01), suggesting that OH may be an independent factor for worse rehabilitation outcomes. To test this hypothesis, we conducted univariate and multivariate regression analyses in the adult patients (n=8146) of this cohort to include other potential factors affecting ΔLOS and FIM efficiency (age, sex, diagnosis of admission and comorbidities grouped into 22 categories by organ systems). We found that OH was independently associated with a longer than predicted LOS (i.e. greater ΔLOS) and lower FIM efficiency (regression coefficient 2.2±0.5 and -0.4±0.1, respectively; P<0.01). These associations remained significant after adjusting for predicted LOS and FIM on admission, suggesting that the effects of OH were not accounted for in these metrics. Other factors significantly associated with greater ΔLOS and lower FIM efficiency were comorbidities associated with the urinary tract, gastrointestinal and peripheral nervous systems, infections, electrolyte imbalance and pressure ulcers. In conclusion, OH has a major independent negative effect on rehabilitation outcomes, and is associated with longer than predicted inpatient rehabilitation LOS and lower functional gain. We suggest that the presence of OH should be considered when setting up the rehabilitation plan, to include management of OH.