Chemotherapeutics used in cancer treatment may elicit pleiotropic effects interfering, for instance, directly on DNA metabolism or on endoplasmic organelles functions. Recently there has been a trend towards the use of molecular-targeted therapies as alternative treatments of cancer, arising from the need to overcome the onset of undesired side effects or drug-resistance. Thus, a major challenge is the design and synthesis of new agents able to interact with specific cellular components, often over-expressed or altered in cancerous cells, such as telomerase and topoisomerase or protein kinases, with reduced toxicity at effective doses. The main molecular targets for the development of new anticancer drugs include: cell surface receptors, signal transduction pathways, enzymes, gene transcription, ubiquitin-proteasome/heat shock proteins, and anti-angiogenic agents. Several natural or synthetic polycyclic molecules with carbazolic nucleus, which show attractive drug-like properties, were identified with the aim to increase their biological activities and their specificity, obtaining cytotoxic agents effective in a panel of cancer cell lines. The cytotoxic profile of these compounds has been assessed using several in vitro assays as, for instance, MTT, colony formation, and flow cytometry assays and some of these compounds showed an interesting profile at sub-micromolar concentrations. The usefulness of some carbazole derivatives has been demonstrated, as well, in preclinical studies.