Objective: To study the link between free thyroxine (FT4) levels and mortality in hypertensive patients. Methods: Utilizing data from the National Health and Nutrition Examination Survey performed in the United States from 2007 to 2012. Results: This study included 3365 adults from the National Health and Nutrition Examination Survey (NHANES) 2007–2012. Weighted Cox regression model, Kaplan-Meier (KM) survival analysis, and restricted cubic spline (RCS) were used to analyze the link between FT4 levels and mortality in hypertensive patients. Furthermore, subgroup analyses and interaction analyses were carried out to evaluate the stability of links between FT4 levels and all-cause mortality across different subgroups of hypertensive patients. In the weighted Cox regression model, after adjusting for all covariates, FT4 levels treated as a continuous variable were positively linked to all-cause mortality in hypertensive patients (HR = 1.08,95% CI: 1.04-1.12, P