Resistant hypertension (RH) is characterized by uncontrolled blood pressure (BP) despite optimal antihypertensive treatment. This study investigated the clinical characteristics and target organ damage (TOD) in patients with RH, examining their relationships with BP and heart rate variability (HRV). Among 386 hypertensive patients-including those with RH, controlled hypertension, and inadequately treated hypertension-clinical data, laboratory results, and 24-h ambulatory BP monitoring were analyzed. Patients with RH showed higher body mass index, blood glucose, serum uric acid levels, and longer hypertension duration compared to other groups. Notably, in patients with uncontrolled RH, markers of TOD such as urinary albumin-creatinine ratio and pulse wave velocity measures were significantly elevated. Multivariate regression revealed that earlier onset of hypertension, elevated serum uric acid and creatinine, and increased arterial stiffness independently predicted RH. Additionally, TOD indicators were closely correlated with 24-h systolic and diastolic BP as well as HRV parameters. Increased BP variability and arterial stiffness were identified as important factors contributing to TOD, suggesting a bidirectional relationship that may hasten disease progression. These findings emphasize that RH is strongly associated with severe TOD, particularly when BP remains uncontrolled. Effective management of both BP levels and their variability is essential to reduce TOD, and further studies are needed to clarify underlying mechanisms and improve therapeutic strategies.