Nanodiamonds form a dynamic protein corona independent of the type of surface functional group. Proteomics data suggest that the top 30 proteins of nanodiamonds that are incubated in fetal bovine serum are similar in terms of abundance and function, despite differences in the nanodiamond surface properties. Surprisingly, the most abundant serum protein, albumin, is not one of the most abundant corona proteins, with low molecular weight proteins below 20 kDa being favoured. The pre-incubation of a protein corona on nanodiamonds significantly decreases the production of reactive oxygen species, increasing the cell viability of macrophages after incubation with the nanodiamonds for 48 hours. However, this effect was only observed for protein coronas on nanodiamonds with a negative surface charge and not when they were functionalised with positive surface charges, such as amine groups. This work highlights the role of the protein corona in colloidal stability and its effect on the biological behaviour of diamond nanoparticles.