Food grade proteins can be viewed as an adequate material for the preparation of nanoparticles and microparticles. They offer several advantages such as their digestibility, price and a good capability to interact with a wide variety of compounds and nutrients. The aim of this work was to prepare and characterize casein nanoparticles for the oral delivery of folic acid. These nanoparticles were prepared by a coacervation process, stabilized with either lysine or arginine and, finally, dried by spray-drying. For some batches, the effect of a supplementary treatment of nanoparticles (before drying) with high hydrostatic pressure on the properties of the resulting carriers was also evaluated. The resulting nanoparticles displayed a mean size close to 150 nm and a folic acid content of around 25 ¿g per mg nanoparticle. From the in vitro release studies, it was observed that casein nanoparticles acted as gastro-resistant devices and, thus, folic acid was only released under simulated intestinal conditions. For the pharmacokinetic study, folic acid was orally administered to laboratory animals as a single dose of 1 mg/kg. Animals treated with folic acid-loaded casein nanoparticles displayed significantly higher serum levels than those observed in animals receiving an aqueous solution of the vitamin. As a consequence the oral bioavailability of folic acid when administered as casein nanoparticles was calculated to be around 52%, a 50% higher than the traditional aqueous solution. Unfortunately, the treatment of casein nanoparticles by high hydrostatic pressure modified neither the release profile of the vitamin nor its oral bioavailability.