DAF-16/forkhead transcription factor, the downstream target of the insulin-like signaling in Caenorhabditis elegans, is indispensable for both lifespan regulation and stress resistance. Here, we demonstrate that c-Jun N-terminal kinase (JNK) is a positive regulator of DAF-16 in both processes. Our genetic analysis suggests that the JNK pathway acts in parallel with the insulin-like signaling pathway to regulate lifespan and both pathways converge onto DAF-16. We also show that JNK-1 directly interacts with and phosphorylates DAF-16. Moreover, in response to heat stress, JNK-1 promotes the translocation of DAF-16 into the nucleus. Our findings define an interaction between two well conserved proteins, JNK-1 and DAF-16, and provide a mechanism by which JNK regulates longevity and stress resistance.