A new nanodrug system containing bis(menthone thiosemicarbazonato) Platinum(II) complex (Pt-thiomen) encapsulated with the block copolymers polylactide-d-α-tocopheryl polyethylene glycol 1000 succinate (PLA-TPGS) was prepared by a modified solvent extraction/evaporation technique. The characteristics of the nanoparticles including surface morphology, size distribution, structure, and biological activities such as antimicrobial and cytotoxic activities were in vitro investigated. The spherical nanoparticles were around 50 nm in size with core-shell structure and narrow-size distribution. The encapsulated Pt-thiomen can avoid interaction with proteins in the blood plasma. The inhibitory activity of Pt-thiomen-loaded PLA-TPGS nanoparticles on the growth of some bacteria, fungi, and Hep-G2 cells suggests a possibility of developing PLA-TPGS-Pt-thiomen nanoparticles as one of the potential chemotherapeutic agents.