Poly I:C is a synthetic dsRNA that can imitate a viral infection and elicit host immune responses by triggering specific pattern-recognition receptors (PRRs) such as toll-like receptor 3 and retinoic acid inducible gene I(RIG-I)-like receptors, including RIG-I and melanoma differentiation-associated gene 5. Activation of these PRRs by poly I:C triggers a signal transduction cascade that results in the activation of NF-κB and production of type I interferon. Poly I:C has been used as a vaccine adjuvant for cancer immunotherapy for several decades. Evidence from recent studies indicates that poly I:C can directly induce apoptosis in several types of tumor cells, thus providing a new therapeutic approach for cancer treatment. However, the molecular mechanism underlying the induction of apoptosis by poly I:C is still unclear. In this review, we summarize the current knowledge of poly I:C-induced tumor cell apoptosis, focusing on the key molecules and pathways involved in this process.