c‐Jun N‐terminal kinase (JNK) is involved in cancer cell apoptosis; however, emerging evidence indicates that this Janus signaling promotes cancer cell survival. JNK acts synergistically with NF‐κB, JAK/STAT, and other signaling molecules to exert a survival function. JNK positively regulates autophagy to counteract apoptosis, and its effect on autophagy is related to the development of chemotherapeutic resistance. The prosurvival effect of JNK may involve an immune evasion mechanism mediated by transforming growth factor‐β, toll‐like receptors, interferon‐γ, and autophagy, as well as compensatory JNK‐dependent cell proliferation. The present review focuses on recent advances in understanding the prosurvival function of JNK and its role in tumor development and chemoresistance, including a comprehensive analysis of the molecular mechanisms underlying JNK‐mediated cancer cell survival. There is a focus on the specific “Yin and Yang” functions of JNK1 and JNK2 in the regulation of cancer cell survival. We highlight recent advances in our knowledge of the roles of JNK in cancer cell survival, which may provide insight into the distinct functions of JNK in cancer and its potential for cancer therapy.