Amygdalin is a natural compound primarily found in seeds of fruit trees. In the human body, it is hydrolyzed to benzaldehyde, glucose, and cyanide, which is considered the active component of amygdalin. The semi-synthetic form of amygdalin is known under the commercial name Laetrile® or as vitamin B17. This review aims to provide a comprehensive overview of studies that evaluated the potential therapeutic effects of amygdalin in oncology. Preclinical studies provided information about the mechanisms of action of amygdalin in vitro and in vivo and its toxicity. Recent in vitro studies demonstrated the effects of amygdalin on the cell cycle, apoptosis, and synthesis of cyclooxygenase-2, inducible nitric oxide synthase, E-cadherin, and integrins β1 and β4. However, amygdalin exhibited no or low treatment efficiency in preclinical in vivo studies. Conversely, many case studies describe the anti-tumor effects of amygdalin, but these have not been confirmed in clinical trials. Only two clinical studies published almost 40 years ago focused on the safety of amygdalin administered orally and intravenously. Although these studies reported that amygdalin had no benefit in 178 cancer patients, this compound has recently come to the attention of both scientists and patients. The results of recent in vitro studies are promising and indicate that amygdalin has a oncopreventive effect, although this must be confirmed by in vivo studies and clinical trials. Considering its proven toxicity and unconvincing clinical effects, amygdalin cannot currently be recommended to oncology patients as a supportive treatment.