Photodynamic therapy (PDT) and bio-nanotechnology (NT) show striking similarities in clinical design and mechanistics. The PDT paradigm of photosensitizer application, light activation and singlet oxygen generation does in fact occur on the nanoscale level as does the resultant outcomes. NT has the ability to explain as well as modify each of the critical steps of PDT particularly photosensitizer design and delivery, light source miniaturization and optimization, location and intensity of the photodynamic reaction as well as offering a far greater insight into dosimetry and mechanisms of action. This review will explore the current and potential future interactions and modifications NT may have on PDT.