The aim of this work was to produce and characterize triclosan-loaded nanoparticles (NPs) by the emulsification-diffusion process, in an attempt to obtain a novel delivery system adequate for the treatment of periodontal disease. The NPs were prepared using poly(D,L-lactide-co-glycolide) (PLGA), poly(D,L-lactide) (PLA) and cellulose acetate phthalate (CAP). Poly(vinyl alcohol) (PVAL) was used as stabilizer. Batches were prepared with different amounts of triclosan (TCS) in order to evaluate the influence of drug on NP properties. Solid NPs of less than 500 nm in diameter were obtained. Entrapment efficiencies were higher than 63.8%. The characterization by scanning electron microscopy and light scattering indicated that high concentrations of TCS seemingly caused the increase of NP mean size. A decrease in the PLGA glass transition temperature was observed by differential scanning calorimetry. This could indicate that TCS in PLGA-NPs behaves as a non-conventional plasticizer. Subsequently, in vitro release studies were carried out under sink conditions using a device designed in our laboratory to allow a direct contact between the particles and the dissolution medium. A fast release of TCS from NPs was detected. A preliminary in vivo study in dogs with induced periodontal defects suggested that TCS-loaded NPs penetrate through the junctional epithelium.