This work reports on the preparation of UV-light responsive nanocapsules based on cross-linked polyamide, obtained by miniemulsion interfacial polymerization. The photo-triggered E-Z transition of azobenzene moieties of the polymer backbone enabled controlled release of encapsulated molecules. Appropriate selection of emulsion conditions allowed tailoring size distribution of the resulting nanocapsules. The light responsiveness of the nanocapsule systems has been evaluated by monitoring size change and release of a fluorescent probe upon UV irradiation, and an unambiguous relationship between capsule size and release kinetics has been highlighted. In particular, the smaller the capsule size, the faster the achieved release. Therefore, the photoresponsiveness of the nanosized capsule systems can be modulated by a proper selection of emulsion and processing parameters. The significance of the reported results lies in the size control of the encapsulating particles, which in turn enables to tailor their swelling kinetics, and to precisely design light-controlled release systems. (C) 2015 Elsevier Ltd. All rights reserved.