Conductive films that are both stretchable and flexible could have applications in electronic devices(1,2), sensors(3,4), actuators(5) and speakers(6). A substantial amount of research has been carried out on conductive polymer composites(7), metal electrode-integrated rubber substrates(8-10) and materials based on carbon nanotubes and graphene(1,2,11-13). Here we present highly conductive, printable and stretchable hybrid composites composed of micrometre-sized silver flakes and multiwalled carbon nanotubes decorated with self-assembled silver nanoparticles. The nanotubes were used as one-dimensional, flexible and conductive scaffolds to construct effective electrical networks among the silver flakes. The nanocomposites, which included polyvinylidenefluoride copolymer, were created with a hot-rolling technique, and the maximum conductivities of the hybrid silver-nanotube composites were 5,710 S cm(-1) at 0% strain and 20 S cm(-1) at 140% strain, at which point the film ruptured. Three-dimensional percolation theory reveals that Poisson's ratio for the composite is a key parameter in determining how the conductivity changes upon stretching.