Discrete polymers offer an excellent platform for comprehending the interplay between precise chain structures, distinctive self-assembly behavior, and functional applications, whereas the development of discrete polymers with self-immolative properties remains scarce. Here, we modularly synthesize a library of discrete self-immolative oligourethanes containing N-naphthylcarbamate or N-(3-fluorophenyl)carbamate repeating units via iterative stepwise growth. These oligourethanes undergo not only cascade 1,6-elimination depolymerizations via photo-mediated removal of o-nitrobenzyl carbamate triggers but also selective cleavage of benzyl-O linkages under MS/MS conditions even without UV light irradiation. In aqueous media, these discrete oligourethanes self-assemble into different morphologies such as flat nanosheets, nanofibers, and nanoribbons, depending on the chain lengths and backbone compositions, and further morphological transitions are observed upon thermal annealing.