The delta Cd-114/110 values of thirty-four environmental and geological reference materials, including rocks, sediments, soils and biological samples, were determined on a Neptune Plus MC-ICP-MS instrument using a Cd-111-Cd-113 double spike technique. An intermediate measurement precision of better than +/- 0.074 parts per thousand (2s) was achieved with different reference materials (RMs) of highly variable matrices and Cd contents. The uncertainty of delta Cd-114/110 values was assessed by calculating the 95% confidence interval of the results from this study and the literature using Student's t-test. Our measurements of nine previously analysed RMs yielded delta Cd-114/110 values that were indistinguishable from previous results. New reference values for the thirty-four geological and biological RMs are reported here. The comprehensive data set for these RMs provides guidelines for quality assurance and inter-laboratory comparison for Cd isotope determination. The large range of delta Cd-114/110 values in rock (-0.001 to +0.287 parts per thousand) and biological RMs (-0.806 to +0.142 parts per thousand) suggests that Cd isotope ratio measurement results are a useful tool to study biogeochemical processes.