‘Biosecurity’ describes methods of reducing the risk of disease spread. Two defining aspects of organic farming are the requirement to allow animals outside access and the aim to nurture animal health without reliance on veterinary medicines. These measures create differences in risks of disease and access to environmental pollutants compared to non-organic animals. This chapter summarises some of the biosecurity issues particular to organic farming and discusses their significance to human health. Particular focus is given to organic animal rearing and the unique challenges of this sector. A number of strategies for reducing risk of infectious disease are discussed, and two case studies are presented to show how biosecurity has been addressed in practice. It is concluded that applying bespoke biosecurity plans on farms can reduce animal disease risk, thereby increasing the health and welfare of farmed animals and contributing to high standards of food quality.