The social demand for novel, sustainable and environment friendly approaches, while ensuring the health and productivity of our crops, is increasingly growing. Research on biological control of tree/woody crop diseases is scarce compared to that conducted on herbaceous, annual plants. In addition to their large biomass, complicated anatomy, longevity and perennial nature, peculiarities in the management of tree crops and forestry also contribute to the complexity of the processes of developing effective biological control measures in these agro-ecosystems. Although biological control in woody species poses challenges, difficulties and limitations, its implementation either alone or in combination with other disease management strategies is feasible. As a result, examples of successful application of biocontrol measures based on the use of bacteria, fungi or hypovirulent mycoviruses against tree/woody plant diseases are available. The aim of this special issue is to provide interested readers with an overview and updates on the active research field of biological control of tree and woody plant diseases. Such effort includes updates ranging from the generation of fundamental knowledge to examples of successful application of biological control strategies.