Biological control is an underlying pillar of integrated pest management, yet little focus has been placed on assigning economic value to this key ecosystem service. Setting biological control on a firm economic foundation would help to broaden its utility and adoption for sustainable crop protection. Here we discuss approaches and methods available for valuation of biological control and summarize economic evaluations in classical, augmentative and conservation biological control of arthropod pests by arthropod natural enemies. Emphasis is placed on valuation of conservation biological control, which has received very little attention. We identify some of the constraints, challenges and opportunities for applying biological control economics to advance IPM. Interaction among diverse scientists and stakeholders will be required to measure the direct and indirect costs and benefits of biological control that will allow farmers and others to internalize the benefits that incentivize and accelerate adoption for private and public good.