The effective thermal conductivity of composites made up of silver micro-particles embedded in a resin matrix is modelled and measured. This is done for spherical and flake-like particles to analyse the effects of the particles geometry and concentration on the composite thermal performance. It is experimentally found that spherical particles yield a higher thermal conductivity than the one given by flakes, such that it takes the value of 16Wm-1K-1for a 50% volume fraction of particles. Furthermore, this behaviour is well described by a simple and analytical model, which takes into account the particle-particle interactions through a crowding factor. The obtained results could be useful to optimize the design and manufacture of composites with metallic particles.