Abstract (PDF) Graphical Abstract: Heterobranchs are a fascinating group of marine mollusks that are recognized as an important source of bioactive natural products. Often, these molecules, which are either selected from the diet or de novo biosynthesized by the mollusks, play a fundamental role for their survival being utilized as defensive chemicals against predators. A summary of the studies carried out, in the last decade, on heterobranchs is presented here. A number of new compounds exhibiting different molecular architectures were chemically characterized.