BACKGROUND: Frailty frequently coexists with hypertension in older patients. We aimed to evaluate the association between frailty and positional change in blood pressure, especially orthostatic hypertension. METHODS: Participants were recruited from 12 University hospitals in South Korea. Using a digital device, trained research nurses measured blood pressure in the supine and standing positions. Physical frailty was evaluated using the Korean version of the FRAIL questionnaire, gait speed, and handgrip strength. Orthostatic hypertension was defined as a ≥20-mm Hg increase in systolic blood pressure within 3 minutes of standing and upright systolic blood pressure of ≥140 mm Hg. RESULTS: We analyzed the data of 2065 participants who had been enrolled until December 31, 2022. The mean age was 73.2±5.6 years, and 52.0% were female. The mean blood pressure was 137.1±14.9/75.1±9.7 mm Hg. Among the participants, 1886 (91.3%) showed normal response after standing, but 94 (4.6%) had orthostatic hypertension, and 85 (4.1%) had orthostatic hypotension. Orthostatic hypertension was associated with female sex, obesity, cognitive function, physical frailty, and lower quality of life. In the multivariable analysis, body mass index and frailty status were independently associated with orthostatic hypertension. CONCLUSIONS: Orthostatic hypertension is associated with physical frailty, cognitive impairment, and low quality of life in older patients with hypertension. Therefore, evaluation of orthostatic blood pressure changes to confirm orthostatic hypertension or hypotension in frail older adults will serve as an important diagnostic procedure in vulnerable patients. Further studies are required to identify the underlying mechanisms of this association.