Aquaculture stands out as one of the rapidly expanding domains within the food industry with a global annual growth rate of around 11%, supplying over 16% of the world’s animal protein, mostly for human consumption. It is an indispensable part of the economy of most developing countries. The growth of aquaculture and the consecutive increase in the transboundary movement of live and processed aquatic organisms have been attributed to an increase in the spread of diseases. In the realm of animal husbandry, the term biosecurity is commonly employed to describe the preventative measures implemented to safeguard against infectious diseases. It can be defined as “a set of standard scientific measures adopted to exclude pathogens (prevent the establishment and spread of pathogens) from the host and the rearing environment”. Appropriate biosecurity measures can curb diseases and monetary losses in aquaculture. Biosecurity measures in farms and hatcheries should be maintained at the entry, internal as well as exit levels to ensure complete control over the health management. Standard biosecurity procedure involves key steps such as hazard identification, risk assessment and risk management. In general, the programme involves practices and procedures involving preventive methods such as quarantine, certification and vaccination, monitoring of organisms as well as the system, disinfection and disease treatment. Overall sustainability of the aquaculture depends on the biosecurity measures and best management practices followed by hatchery/grow-out operators and exporters. This chapter discusses various methods adopted to ensure biosecurity at different levels in farms and hatcheries such as quarantine, health certifications including SPF and SPR, vaccination, disease surveillance, system management, effluent treatment and various legislative measures developed by different agencies, organizations or nations.