The non-relativistic and four-component fully relativistic calculations of 1H, 15N, 59Co, 103Rh, and 193Ir shielding constants of pentaammineaquacomplexes of cobalt (III), rhodium (III), and iridium (III) were carried out at the DFT level of theory. The noticeable deshielding relativistic corrections were observed for nitrogen shielding constants (chemical shifts), while those corrections were found to be negligible for protons. For the transition metals cobalt, rhodium, and iridium, relativistic corrections to their NMR shielding constants were found to be rather small for cobalt and rhodium (some 5-10%), while they are essentially larger for iridium (up to 70%).