Interest in temperate agroforestry has increased substantially over the past several years because of its potential as an environmentally positive, sustainable, and potentially profitable set of land use practices. Knowledge of the complex interactions among trees, crops and their associated fauna is necessary to determine the viability of a particular agroforestry practice. While a significant amount of research has been conducted on the ecological interactions among components of tropical agroforestry practices, little information is available on these interactions in the temperate regions of the world. Agroforestry’s effect on insect populations, both pests and beneficials, in temperate alley cropping practices is particularly lacking. Theoretically, agroforestry holds promise for increasing insect diversity and reducing pest problems by improving natural enemy complexes and adding competition to pest species. We discuss the theories behind agroforestry’s potential to ameliorate pest problems. Examples from our research on alfalfa pests in a temperate black walnut-alfalfa alley cropping practice demonstrate a reduction in herbivore numbers and an increase in natural enemy numbers for the agroforestry practice versus the traditional agricultural practice.