Plant-derived secondary metabolites (SMs) have been the major focus globally due to their beneficial industrial and pharmaceutical applications. Having well-productive biomass and a diverse ecosystem, mangrove plants contain diverse classes of bioactive metabolites that have enormous significance in the area of bioactive compounds of health and industrial significance. The present chapter highlights the SMs found in a mangrove plant Sesuvium portulacastrum and the SM-associated biological activities. A detailed phytochemical profile is shown for the SMs isolated from S. portulacastrum. There have been several studies reporting the bioactivities of isolated SMs and/or crude extracts of S. portulacastrum extracts, such as antimicrobial, anticancer, insecticidal, antioxidant, hypolipidemic, antidiuretic, anti-inflammatory, hepatoprotective, and immunoprotective properties. Research efforts have been made in the past two decades to determine the biologically active metabolites of S. portulacastrum which can be utilized for healthcare. These natural bioactive metabolites have demonstrated their antimicrobial actions towards human, animal, and plant pathogens. The chapter provides a discussion on the bioactive metabolites of S. portulacastrum and other mangroves, their biopotency, and, a perspective on the SMs in future drug discovery research. Identification of S. portulacastrum phytometabolites and characterization of the biological activities offer scope for discovering novel therapeutic agents.