We report the successful deposition of mono- and multilayers of azopoly-L-lysine (APLL), a synthetic polypeptide to which an azobenzene moiety has been added as a side chain. Such a molecule in solution shows phototropism, due to light-induced trans-cis isomerization. The Langmuir-Blodgett (LB) deposition was difficult due to the very high viscosity of the Langmuir monolayer; we were able however to deposit homogeneous films up to seven layers. Optical absorption studies showed linearity between the optical density and the number of layers. Our main result is that the phototropism of the APLL is preserved in the solid LB film. Under ultraviolet illumination with a 400 W Xe lamp, we found photoconversion of up to 30% in optical density. Preliminary relaxation measurements showed a back-relaxation time of the order of 24 h. These results make APLL an interesting system for optoelectronic applications.