In this study, we measured natural isotopic variation of terrestrial nickel using multiple-collector inductively coupled plasma mass spectrometry. External precisions in ⁵⁸Ni/⁶²Ni, ⁶⁰Ni/⁶²Ni, ⁶¹Ni/⁶²Ni, and ⁶⁴Ni/⁶²Ni ratios of 0.02%, 0.01%, 0.04%, and 0.09% (2 × standard deviation), respectively, were routinely obtainable for a Ni isotopic reference standard by correcting the mass discrimination effect with a ⁶⁵Cu/⁶³Cu ratio of 0.4456. Only a small isotopic variation of ±0.15‰ amu⁻¹ was observed among seven commercially available reagent-grade nickel metals, while variation of ±0.20‰ amu⁻¹ was observed for two nickel sulfide samples from Canada. The isotopic compositions of the two types of samples overlap. The overall variation of ±0.25‰ amu⁻¹ corresponds to an uncertainty of 0.000 37 for the atomic weight of nickel; this uncertainty is twice the currently recommended value (56.6934 ± 0.0002) for the standard atomic weight of terrestrial nickel as proposed by IUPAC.