Biosilica from living diatom microalgae has recently attracted the interest of the scientific community and found several applications in bio-nanotechnology. Among silica-maker organisms, diatom microalgae represent the most attractive marine microorganisms, featuring highly hierarchical, nanotextured and porous silica walls. These biologic structures, known as “frustules” are also chemically addressable via simple chemical synthesis. In this work, we propose new diatom-based hybrid materials consisting of biosilica extracted from living Thalassiosira weissflogii coated with polydopamine (PDA) films. The adhesion properties of the PDA were exploited to decorate the silica surface with silver nanoparticles. These multifunctional heterostructures can be useful for applications ranging from bioelectronics to biomedicine.