Carotenoids being most important pigments among those occurring in nature, have received increased interest owing to their beneficial effects on human health. An effort is made to review marine carotenoids as important bioactive compounds with reference to their presence, chemical, and biofunctional benefits they afford. The potential beneficial effects of marine carotenoids were particularly focused on astaxanthin and fucoxanthin, major marine carotenoids found in marine animals and aquatic plants, respectively. Both carotenoids show strong antioxidant activity which is attributed to quenching singlet oxygen and scavenging free radicals. The potential role of the carotenoids as dietary antioxidants has been suggested as being one of the main mechanism by which they afford their beneficial health effects such as anticancer activity and anti-inflammatory effect. Only recently, antiobesity effect and antidiabetic effect have been noted as specific and novel bio-functions of fucoxanthin. Nutrigenomic study reveals that fucoxanthin induces uncoupling protein 1 (UCP1) expression in white adipose tissue (WAT) mitochondria to lead to oxidation of fatty acids and heat production in WAT. Fucoxanthin improves insulin resistance and decreases blood glucose level, at least in part, through the down-regulation of tumor necrosis factor $alpha$ ($TNF{alpha}$) in WAT of animals.