Constituents of marine algae gained importance in the last four decades due to the growing interest in their potential for medicinal use. Till today, 44 alkaloids were isolated from macroalgae, some of which were reported to induce important pharmacological effects. These alkaloids can be classified under four groups as 2-phenylethylamine, indole, halogenated indole, and 2,7-naphthyridine derivatives, and each group displays a relatively distinguished activity profile. Overall, pharmacological effect spectrum of macroalga alkaloids is wide and includes neuromodulation, neurotransmission, growth regulation, cytotoxicity, angiogenesis, antioxidation as well as antibacterial, antifungal, and larvicidal activities.