Connexins play important roles in many physiological and pathological processes. Although connexins are considered as tumor suppressors in several types of cancer, their roles in pancreatic cancer are unknown. In this study, we found that connexin 43 (Cx43) caused apparent apoptosis and growth inhibition in pancreatic cancer cells. The tumor-suppressive role of Cx43 was independent of the canonical gap junction pathway. In the context of apoptosis, Cx43 translocated to the mitochondria, where it interacted with Bax to initiate the mitochondrial apoptotic pathway. Following further examination of the Cx43 protein, we found that the 241-382aa region of Cx43 was required for interaction with Bax. Furthermore, this region was responsible for permeabilizing mitochondrial membrane potential. The results from the present study elucidate a novel mechanism of the Cx43-mediated regulation of apoptosis in pancreatic cancer.