Clonostachys rosea is a fungal biocontrol agent which has the capacity to manage a wide range of plant pathogens which affect numerous economically important crops such as cereals, vegetables, berries and others. This chapter will focus on the applied use of C. rosea in agriculture, including its diverse mechanisms of action and how it has been applied to effectively manage crop diseases. Some of the variables that alter the efficacy of C. rosea as a biocontrol agent will also be discussed. Although the research and practical use of C. rosea has predominantly focused on its ability to manage plant disease, there is emerging research showing that it may also be effective at controlling plant parasitic nematodes, as well as insects. These pests may damage crops and act as vectors of plant diseases. The study of C. rosea has elucidated many genetic components that underline its biocontrol mechanisms and the capabilities of other biocontrol agents. This may in turn lead to more targeted and effective use of C. rosea to manage plant diseases. C. rosea may also be utilized alongside other disease management approaches in an integrated pest management strategy, which may enhance the efficacy of the entire program. Although topics such as the genetic components of biocontrol are discussed in this chapter, it does not offer a comprehensive overview of subjects such as this, rather it is meant to briefly introduce their relevance to the biocontrol abilities of C. rosea.