Objectives: Kidney volume is used as predictive and therapeutic marker for several clinical conditions. However, there is a lack of large-scale studies examining the relationship between kidney volume and various clinicodemographic factors, including kidney function, body composition, and physical performance. Methods: In this observational study, MRI-derived kidney volume measurements from 38,526 UK Biobank participants were analyzed. Major kidney volume-related measures included body surface area (BSA)-adjusted total kidney volume (TKV) and the difference of bilateral kidneys. Multivariable-adjusted linear regression and cubic spline analyses were used to explore the association between kidney volume-related measures and clinicodemographic factors. Cox or logistic regression was used to identify the risks of death, non-kidney cancer, myocardial infarction, ischemic stroke, and chronic kidney disease (CKD). Results: The median of BSA-adjusted TKV and difference in kidney volume were 141.9 (128.1–156.9) mL/m2 and 1.08 (1.04–1.15) fold, respectively. Higher BSA-adjusted TKV was significantly associated with higher eGFR (beta [95% CIs], 0.43 [0.42–0.44]; P < 0.001), higher composition of muscle volume (beta [95% CIs], 0.50 [0.48–0.51]; P < 0.001), and higher mean handgrip strength (beta [95% CIs], 0.15 [0.13–0.16]; P < 0.001), while associated with lower visceral adipose tissue volume (VAT, beta [95% CIs], -0.09 [-0.11 – -0.07]; P < 0.001) in adjusted models. Higher difference in bilateral kidney volumes was associated with lower eGFR, muscle volume, and physical performance, while associated with higher proteinuria and VAT. Higher BSA-adjusted TKV was significantly associated with the reduced risk of CKD (odds ratio [OR], 0.7 [0.63–0.77]; P < 0.001), while higher difference in kidney volume was significantly associated with increased risk of CKD (OR, 1.13 [1.07–1.20]; P < 0.001). Conclusions: Higher BSA-adjusted TKV and lower discrepancies in bilateral kidney volumes are associated with higher kidney function, muscle volume, physical performance, and reduced risk of CKD.