To study whether sleep blood pressure (BP) self-measured at home is associated with organ damage, the authors analyzed the data of 2562 participants in the J-HOP study who self-measured sleep BP using a home BP monitoring (HBPM) device, three times during sleep (2 am, 3 am, 4 am), as well as the home morning and evening BPs. The mean sleep home systolic BPs (SBPs) were all correlated with urinary albumin/creatinine ratio (UACR), left ventricular mass index (LVMI), brachial-ankle pulse wave velocity (baPWV), maximum carotid intima-media thickness, and plasma N-terminal pro-hormone pro-brain-type natriuretic peptide (NTproBNP) (all P<.001). After controlling for clinic SBP and home morning and evening SBPs, associations of home sleep SBP with UACR, LVMI, and baPWV remained significant (all P<.008). Even in patients with home morning BP <135/85 mm Hg, 27% exhibited masked nocturnal hypertension with home sleep SBP ≥120 mm Hg and had higher UACR and NTproBNP. Masked nocturnal hypertension, which is associated with advanced organ damage, remains unrecognized by conventional HBPM.