Nanotechnology has begun to play a remarkable role in various fields of science and technology. In biomedical applications, nanoparticles have opened new horizons, especially for biosensing, targeted delivery of therapeutics, etc. Among drug delivery systems (DDSs), smart nanocarriers that can respond to specific stimuli in their local environment represent a growing field. Nanoplatforms that can be activated by an external application of light, can be used for a wide variety of photo-activated therapies, (especially light-triggered DDSs) relying on photo-isomerization, photo-crosslinking/uncrosslinking, photo-reduction, etc. In addition, light activation also has potential in photodynamic therapy (PDT), photothermal therapy (PTT), radiotherapy, protected delivery of bioactive moieties, anti-cancer drug delivery systems, theranostics (i.e. real-time monitoring and tracking combined with a therapeutic action to different diseases sites and organs). Combinations of these approaches can lead to enhanced and synergistic therapies, employing light either as a trigger for release or for activation. Non-linear absorption mechanisms using deeply penetrating near-infrared light, such as two-photon absorption, and photon upconversion have been employed in the design of light-responsive DDSs. The integration of a light stimulus into dual/multi-responsive nanocarriers can provide both spatiotemporal controlled delivery and release of therapeutic agents. Targeted and controlled nanosystems combining delivery of two or more agents, can provide on-demand release under specific conditions, etc. Overall, light activated nanomedicines and DDSs are expected to provide more effective therapies against serious diseases such as cancers, inflammation, infections, and cardiovascular disease, with reduced side effects, and will open new doors toward treatment of patients throughout the world.