Objectives: While nocturnal blood pressure non-dipping (NBPD) is associated with poorer cardiovascular outcomes, the clinical significance of the nocturnal heart rate dipping (NHRD) is unknown. Since blood pressure (BP) and heart rate (HR) are modulated by the sympathetic nervous system and may concurrently contribute to the clinical outcomes, we aim to examine the association between HR and BP nocturnal dipping. Methods: A single-center cross-sectional study including living kidney donors (LKD) donating kidneys in 2021 and undergoing pre-donation 24-hour ABPM was conducted to evaluate the association between pre-donation NHRD and NBPD by multiple linear regression. Results: Of all 14 LKD, mean±SD was 44±12 and 50% were female. Mean HR and BP during awake and sleep periods were shown in table 1. Mean±SD NHRD was 10±8%. Percent dipping of systolic and diastolic were 11±6% and 16±9%, respectively. Every 1% increase in NHRD was significantly associated with 0.42% greater nocturnal systolic dipping (βsystolic 0.42, SE 0.18, P 0.037, 95%CI 0.03, 0.82) and 0.41% higher nocturnal diastolic dipping but not statistically significant (βdiastolic 0.41, SE 0.28, P 0.172, 95%CI -0.20, 1.02) (Figure 1). After adjusting for age (≤45 vs >45 y/o), gender, ethnicity, adjusted creatinine clearance, 24-hour dietary sodium and potassium intake, and the interaction term between age and the 24-hour dietary sodium intake (<4 vs. ≥4 g/day), the nocturnal systolic dipping was significantly increased to 0.64% for every 1% increase in NHRD  (βadjusted systolic 0.64, SE 0.24, P 0.043, 95%CI 0.03, 1.24); while the magnitude of the HR – diastolic nocturnal dipping association was even higher but it was not statistically significant (βadjusted diastolic 0.78, SE 0.37, P 0.089, 95%CI -0.17, 1.72). Conclusions: NHRD was positively associated with nocturnal systolic, but not diastolic dipping in healthy LKD. Whether the HR – systolic nocturnal dipping relationship is causal or mediated and in which direction requires further studies.