Forests are inhabited by a variety of insects and pathogens, but invasive alien pests increasingly threaten both natural and commercial plantations worldwide. Biological control is an important component of the management of invasive pests in plantation forests. Biological control involves the use of natural enemies of pests, with the aim of establishing self-sustaining populations capable of reducing pest populations permanently. There are numerous examples of success in the implementation of biological control for forest insects worldwide. However, it still largely remains an empirical practice and its claimed success as a key part of integrated pest management, is often elusive. There are several key ecological concepts and related hypothesis that are important in the implementation and, ultimately, the success of biological control in forest systems. Natural enemy foraging and dispersal behaviour may determine how effective a given natural enemy is in finding and exploiting a pest population and ultimately its long-term effect on the pest populations. Likewise, the relative impact of bottom-up versus top-down forces on pest population dynamics and the dynamic patterns displayed will influence how effective and sustainable agent-induced mortality may be. In turn, adopting the conceptualization of invasion ecology in biological control, may allow a better appreciation of the population-level consequences of the pest- enemy interactions. Generally, ecological processes may prove important to be considered prior to the implementation of biological control of forest pests and may help us to better comprehend successes and failures.