The sensing of protein adsorption by silver nanoparticles/hydroxyapatite composites was investigated using a phosphate buffer solution containing bovine serum albumin (BSA) or lysozyme (LSZ). The adsorption of BSA and LSZ on the composites prepared without using trisodium citrate was similar to plain hydroxyapatite, whereas composites prepared with trisodium citrate showed lower BSA adsorption and higher LSZ adsorption than plain hydroxyapatite powder. Because the ability of the adsorption is mainly governed by surface charges of the powders, the usage of trisodium citrate during the preparation is assumed to produce high negative charges on the surface. The protein adsorption resulted in peak shifts in localized surface plasmon resonance (LSPR) spectra. The peak shifts clearly corresponded to the concentration of the surrounding proteins up to the point of saturation of adsorption on the hydroxyapatite. The silver nanoparticles/hydroxyapatite composites are promising candidate materials for detection of protein adsorption by measurement of LSPR peak shifts, that may be attributed to changes in the dielectric properties of the matrix fluid surrounding the silver nanoparticles.