Cancer is the main cause of death in developing countries. Its development requires multiple steps in which the occurrence of certain events determines the state transition from a normal to a tumor cell. These events are related to the loss of mechanisms that control various biological processes, which results from the accumulation of genetic alterations, including mutations, chromosomal rearrangements, and variations in gene copy number, as well as from epigenetic alterations. In general, chemotherapeutic agents used for toxicity treatments have shown limited antitumor activity, with a high recurrence rate. This has prompted major research efforts to identify novel effective and selective anti-tumor compounds. In this article, we review recent patents that protect the antitumor properties of natural compounds and related molecules derived from plants, animals, or microorganisms. We consider their structure, mechanism of action, molecular targets and, in some cases, the clinical trial phase reached. We also report on various natural agents that appear to prevent cancer development.