Biodegradable polymeric nanocylinders were fabricated by segmental degradation of electrospun nanofibers. Poly(L ‐lactic acid) (PLA) was electrospun to produce non‐crystalline nanofibers that were immediately treated with amino group‐containing strong bases to fabricate semi‐crystalline PLA nanocylinders with tunable aspect ratio. The formation of PLA nanocylinders was attributed to two concurrent events occurring during the aminolysis reaction: (i) development of stacked lamellae and (ii) transversely oriented degradation and fragmentation of the amorphous gaps between lamellae, both responsible for the fragmentation of PLA nanofibers into uniformly shaped nanocylinders. The aspect ratio of PLA nanocylinders was tunable by varying aminolysis time and controlling nanofiber diameter.