Left-handed metamaterials (LHMs) composed of random dendritic cells demonstrate a multi-band resonance and negative refractive index. A nano-assembly approach is established to fabricate optical LHMs. Random nanostructures of silver dendritic cells are prepared and further fabricated into a sandwich-like structure with a dielectric medium. The dentritic nano-assembled configuration reveals a multi-band resonance and a high intensity of the pass-band at infrared frequencies, and can be facilely and cheaply prepared on a large-scale of effective area.