Nanodiamonds (ND) have been gaining impetus in fields such as medicine and electronics. ND has been widely used to modify polymer surfaces and composites for improved functionality. However, there have been limited research on ND application in regard to textile substrates. In this study, we presented a sustainable coating method, adapted to functionalized ND particles that would be coated onto wool fabric surfaces to enhance hydrophilicity. The application of an ND coating was found to increase wool hydrophilicity because of the presence of additional polar groups, shown by Fourier transform infrared spectrometry, which increased surface energy and fiber roughness. Scanning electron microscopy images revealed that the polar ND-coated wool scales demonstrated improved fiber hydrophilicity. Water absorbency, wicking, and contact angle results for coated fabrics confirmed significant improvement in hydrophilicity, which was directly related to the concentration of ND particles. The optimal concentration of ND was therefore selected to coat the wool fabric. Furthermore, tensile strength and abrasion resistance of the coated fabrics were increased due to the exceptional mechanical properties of ND.