BACKGROUND: Postural orthostatic tachycardia syndrome (POTS) is a frequently diagnosed cardiovascular disorder after COVID-19 infection. POTS is characterized by the presence of excessive sinus tachycardia on standing without a fall in blood pressure (BP). We investigated the BP profile using 24-hour ambulatory BP monitoring in patients with new-onset POTS after COVID-19 compared with prepandemic population-based controls. METHODS: We performed a case-control study in 100 patients (mean age, 40.0±12.9 years; 85% women) with verified post–COVID-19 new-onset POTS diagnosed by a positive head-up tilt testing versus 100 controls from a population-based cohort with a negative active standing test, no history of syncope, POTS, or endocrine disease (mean age, 42.3±14.0 years; 78% women). Twenty-four-hour BP profile was assessed for circadian BP variation including hypotensive systolic BP (SBP) episodes (<80, <90, and <100 mm Hg). RESULTS: Patients with post–COVID-19 POTS had significantly higher nighttime SBP, but not daytime SBP, and more daytime SBP hypotensive episodes compared with controls. Nondipping (34% versus 19%; P <0.001) and reverse dipping patterns (9% versus 0%; P <0.001) were more frequent in post–COVID-19 POTS. In the logistic regression, patients with post–COVID-19 POTS had significantly higher mean 24-hour SBP (odds ratio, 1.08 [95% CI, 1.04–1.11]; P <0.001) and nighttime SBP (odds ratio, 1.07 [95% CI, 1.04–1.10]; P <0.001), independent of age and sex. CONCLUSIONS: Patients with post–COVID-19 POTS demonstrate higher mean 24-hour and nighttime SBP and show disruptions of circadian BP rhythm regulation compared with population-based controls, as well as more daytime hypotensive episodes. Future studies are needed to test whether patients with post–COVID-19 POTS may benefit from tailored BP therapy.