Selective H₂ production from formate with Pt nanoparticles dispersed by polyvinylpyrrolidone and cationic biopolymer, poly(L-lysine) (Pt–PVP/PLL), is attempted. Using Pt–PVP/PLL, the highly selective H₂ production based on formate decomposition was accomplished compared with that of Pt–PVP. Moreover, using Pt–PVP/poly(L-glutamic acid), anionic biopolymer, the catalytic activity for selective H₂ production based on formate decomposition was equivalent to that of Pt–PVP. This result suggests that the cationic site of PLL-captured formate ion and promoted the contact with the surface of Pt nanoparticles.