The development of a photo-responsive micellar system capable of triggering cell death is reported. Precursors of the micelles are synthesized by connecting a lipophilic chain to a hydrophilic polyethylene glycol via a photolabile nitrobenzyl group. The resulting amphiphilic units are self-assembled in water forming 12 nm micelles that are readily internalized into cells. Upon photo-irradiation, micelles undergo cleavage and yield a cytotoxic nitrosobenzaldehyde derivative, which significantly inhibits the proliferation of MDA-MB-231 cells under standard in vitro conditions.