Secondary metabolites found in abundance in mangrove plants play a vital role in enabling these plants to withstand challenging environmental circumstances. Over the years, studies on the isolation and characterization of secondary compounds from mangroves have shown that they include a vast number of novel compounds that have not been previously described. Mangrove secondary compounds have been shown to feature unique carbon skeletons, unique ring systems, or peculiar structural moieties. These new substances have also shown a range of biological activity. We reviewed a variety of new compounds in this review, along with their structural variations and biological activity.