Nanomaterial-based biosensors have become one of the major topics in the field of diagnostics. With the growing demand on devices with improved sensitivity and selectivity, rapid response time, and low cost, four categories of nanomaterials have become popular in biosensor research: gold nanoparticles, graphene, carbon nanotubes, and photonic crystals. The ongoing research has brought new designs of biosensors based on nanomaterials, which have greatly improved the potential of field-deployable microfabricated devices. This review describes the recent technologies employing the aforementioned nanomaterials for electrochemical detection of biomolecules, including glucose, DNA, protein, toxins, and so on. We envisage that miniaturized lab-on-a-chip devices employing these nanomaterials will soon be an essential part of our daily life.