Covering: up to January 2020[4 + 2] type terpenoid dimers are natural products biosynthetically derived from [4 + 2] cycloaddition between two terpenoid monomers. They have attracted the attention of scientists due to their complex architectures, biological activities, natural production pathways and synthetic challenges. In this review article, we highlight recent research progress on naturally occurring [4 + 2] type terpenoid dimers, including their sources, bioactivities, biosynthetic hypotheses and total chemical syntheses.