Cancers are a huge threat to human life and health. Every year, many people suffer and die from various cancers, and numerous resources have been used to combat cancer. Due to several disadvantages of anticancer agents, such as drug-induced side effects, drug resistance, etc., there are still wide gaps in their ability to conquer cancer. Therefore, there is an urgent need to discover and develop many novel chemotypes to suppress cancer. In this review, we mainly focus on the anticancer potency of two representative sorts of carbazole-based compounds: carboline derivatives and diazacarbazole derivatives. Diazacarbazole derivatives, which have not been fully explored yet, might bring us a new vision and a valuable opportunity for overcoming the enormous hurdle we are now facing in the cancer campaign. We also provide several synthetic approaches for constructing the critical skeletons of the carbazole-based tricyclic compounds.