This study aims to evaluate the temporal trends of mortality among frail versus non-frail older adult trauma patients during index hospitalization. We performed a 3-year (2017–2019) analysis of ACS-TQIP. We included all older adult (age ≥65 years) trauma patients. Patients were stratified into two groups (Frail vs. Non-Frail). Outcomes were acute (<24 ​h), early (24–72 ​h), intermediate (72 hours-1 week), and late (>1 week) mortality. A total of 1,022,925 older adult trauma patients were identified, of which 19.7 ​% were frail. The mean(SD) age was 77(8) years and 57.4 ​% were female. MedianIQR ISS was 94–10 and both groups had comparable injury severity (p ​= ​0.362). On multivariable analysis, frailty was not associated with acute (aOR 1.034; p ​= ​0.518) and early (aOR 1.190; p ​= ​0.392) mortality, while frail patients had independently higher odds of intermediate (aOR 1.269; p ​= ​0.042) and late (aOR 1.835; p ​< ​0.001) mortality. On sub-analysis, our results remained consistent in mild, moderate, and severely injured patients. Frailty is an independent predictor of mortality in older adult trauma patients who survive the initial 3 days of admission, regardless of injury severity. •Frailty is known as a predictor of worse clinical outcomes and mortality following injury.•The timing of increased mortality rates in frail patients during hospitalization remains unclear.•Frailty is an independent predictor of mortality in older adult trauma patients who survive the initial 3 days of admission.•Early frailty assessment in identifying high-risk individuals is of paramount importance.