A biosensor for detection of nucleic acids employs, as the sensing element, an oligonucleotide, with a known sequence of bases that can be used to detect specific DNA/RNA sequences through the hybridization reaction (this kind of biosensor is also called a genosensor). Many different transducers can be used in the development of a genosensor. Recently, with the emergence of novel photoelectrochemically active species and new detection schemes, photoelectrochemistry has received increasing attention in the field of biosensors. Advances in the development and applications of photoelectrochemical genosensors are reviewed in this article.