β-Carboline alkaloids, including harmine, harmaline, harman, and harmalol, are a diverse group of compounds found in various organisms, including bacteria, algae, fungi, plants, food products, and animal tissues. With over 140 known derivatives, these alkaloids exhibit a wide range of biological activities such as antimicrobial, antiviral, antiparasitic, antioxidant, and anticancer properties. They are effective against several pathogens, including Plasmodium falciparum, Herpes simplex virus, and HIV. Additionally, these alkaloids offer neuroprotective benefits, support memory enhancement, and may be useful in treating neurodegenerative diseases like Alzheimer’s. They also have the potential to regulate melanin production, aiding in the treatment of conditions like vitiligo. Their anti-inflammatory, apoptotic, and antithrombotic effects further broaden their therapeutic applications. Advances in biotechnology, such as tissue culture methods, have significantly enhanced the production of these alkaloids, improving their availability for medical and industrial use.