Marine sponges are primitive metazoans that produce a wide variety of molecules that protect them against predators. In studies that search for bioactive molecules, these marine invertebrates stand out as promising sources of new biologically-active molecules, many of which are still unknown or little studied; thus being an unexplored biotechnological resource of high added value. Among these molecules, lectins are proteins that reversibly bind to carbohydrates without modifying them. In this review, various structural features and biological activities of lectins derived from marine sponges so far described in the scientific literature are discussed. From the results found in the literature, it could be concluded that lectins derived from marine sponges are structurally diverse proteins with great potential for application in the production of biopharmaceuticals, especially as antibacterial and antitumor agents.