Photoreactivity of cyanoacetylene with water was successively studied in cryogenic matrixes and in the solid phase at > 120 nm. These studies were performed using FTIR spectroscopy, isotopic experiments and DFT calculations at the B3LYP/6-31G** level of theory. The photolysis of cyanoacetylene complexed with water in an argon cryogenic matrix led to the formation of two products. The first one corresponds to the cyanoketene and the second to the HCN:C2O complex. Trapped in water ice and submitted to UV photolysis, the cyanoacetylene molecule shows great photoreactivity. Indeed, besides the cyanoketene and cyanhydric acid, we characterized and identified the formation of other compounds issued from the addition of water to the C equivalent to C triple bond of cyanoacetylene.