Diabetes mellitus, a chronic condition that may be life-threatening is a huge threat to the health of people all over the world. Conventional treatments provide only a limited number of remedies, and they often come with unintended consequences. An exceptional opportunity for the development of new anti-diabetic medicines that have strong actions and reduced side effects is presented by the huge marine environment, which has not been investigated to its full potential. Subsequent metabolites derived from marine creatures are the subject of this review, which dives into the fascinating world of secondary metabolites and highlights the many antidiabetic processes and intriguing therapeutic possibilities of these compounds. The secondary metabolites that are produced by marine algae, sponges, fungus, and invertebrates are quite varied in terms of their structural composition. These secondary metabolites include terpenoids, alkaloids, polysaccharides, and polyphenols. One of the effects that these compounds display is the inhibition of α-glucosidase and α-amylase, as well as insulin sensitization and antioxidant activity. These compounds interact with critical targets in glucose metabolism. Phlorotannins, which are found in brown algae can effectively block α-glucosidase, which in turn delays the absorption of glucose. Sterols generated from sea stars have been shown to have insulin-sensitizing effects, whereas alkaloids obtained from fungi are responsible for maintaining glucose homeostasis. Several marine metabolites have made it to the preclinical and clinical testing stages, demonstrating their potential for use in the development of anti-diabetic therapies.