Polyurethane (PU) monomer mixtures containing commercially available o-nitrobenzyl-based photocleavable monomers have been formulated and tested as low-cost positive tone photoresists. The photolysis reaction is studied by UV spectroscopy. Well-defined micropatterns on 2 m thick photodegradable PU films are obtained using 365 nm light exposure. This strategy is also extended to improved formulations based on synthesized o-nitrobiphenylpropyl derivatives with enhanced photochemical properties for single photon excitation and high two-photon absorption cross-sections. Improved pattern resolution in 2D and the capability of 3D resolution using a scanning laser at 780 nm is demonstrated. This work demonstrates the potential of PUs as readily available, versatile, and easy-to-use photoresist materials for low-cost lithography applications.