The design and synthesis of novel hybrid-silica nanoparticles (NPs) containing the FDA-approved antimicrobial triclosan (Irgasan) covalently linked within the inorganic matrix for its controlled, slow release upon interaction, is reported. The NPs are in the range of 130 ± 30 nm in diameter, with a smooth and spherical morphology. Characterization of the hybrid-silica NPs containing triclosan, namely T-SNPs, and their appropriate linkers is accomplished by microscopic and spectroscopic techniques. Preliminary antimicrobial activity is studied through bacterial-growth experiments. The T-SNPs are found to be superior in killing bacteria, as compared with the free biocide.