Jun N-terminal kinases (JNKs) are essential for neuronal microtubule assembly and apoptosis. Phosphorylation of the activating protein 1 (AP1) transcription factor c-Jun, at multiple sites within its transactivation domain, is required for JNK-induced neurotoxicity. We report that in neurons the stability of c-Jun is regulated by the E3 ligase SCF^Fbw7, which ubiquitinates phosphorylated c-Jun and facilitates c-Jun degradation. Fbw7 depletion resulted in accumulation of phosphorylated c-Jun, stimulation of AP1 activity, and neuronal apoptosis. SCF^Fbw7 therefore antagonizes the apoptotic c-Jun–dependent effector arm of JNK signaling, allowing neurons to tolerate potentially neurotoxic JNK activity.