The molecular players regulating the axon degeneration pathway have been identified using in vitro experimental models. Here, we describe an in vitro assay to assess the axonal fragmentation induced by mechanical injury to axons in cultured mouse embryonic dorsal root ganglion (DRG) neurons. DRG neurons are pseudounipolar and therefore suitable for an assay of axonal degeneration after injury. In addition, the time course of the axonal fragmentation is stereotyped, enabling the identification of reagents that either expedite or impede the degeneration process. With an image-based quantification method, the in vitro degeneration assay can be utilized as a platform supporting high-throughput screens for pharmacological or genetic reagents delaying axon degeneration.