Occurrence of pharmaceutically active compounds (PhACs) in marine ecosystems has been confirmed in recent studies. These PhACs include human pharmaceuticals, veterinary medicines and those used in aquaculture . Levels of PhACs in the marine environment are suspected to rise in future due to the increase in anthropogenic activities. This chapter critically discusses the occurrence, sources and fate of PhACs in marine environment. A particular focus has been given to the adverse impacts of PhACs on marine biota and the potential exposure to human. Data related to the distribution of PhACs in seawater , sea sediments and marine biota is presented to elucidate their bioconcentration and bioaccumulation potential. Impacts of PhACs at cellular, molecular and species level are summarised here to understand their mode of action. Lastly, potential biomarkers for effective biomonitoring of marine environment are highlighted to anticipate the risks related to marine ecosystem and human health.