β-Carboline alkaloids are a family of natural and synthetic products with great structural diversity and outstanding biological activities. This review covers critically important developments in the field of β-carbolines, predominantly over the past decade (2006-2017.7). It is focused on both natural and synthetic monomers as well as dimers, and includes key information on occurrence, structural diversity, and biological activities. In the cases where sufficient information is available, structure-activity relationship (SAR) and mechanism of their biological activities were presented. In addition, innovative syntheses of the β-carboline core and potential future directions have been discussed.