The homogenous nature of agricultural landscapes generally reduces biodiversity of invertebrate species, but this can be partly offset by developing refuges at field margins. In Australia, shelterbelts are widely planted to provide protection for livestock and to counter salinity problems associated with rising water tables. Shelterbelts may also play a role in acting as reservoirs for organisms that are beneficial to pastures, although this has rarely been directly evaluated. We sampled invertebrates along transects running from replicated shelterbelts into pastures, and in glasshouse trials we tested the impact of the beneficial organisms from the shelterbelts on the collected pests. Contrary to popular views, numbers of pest mites and lucerne fleas were low within shelterbelts. Moreover, numbers were typically lower adjacent to shelterbelts compared with >30 m into the pasture, an effect that was much more apparent when shelterbelts carried a groundcover of high (>30 cm) grass. Numbers of predatory mites and spiders were higher in shelterbelts and in adjacent pasture when there was taller grass and higher grass cover in the shelterbelts. Samples of potential predators collected from a shelterbelt were more effective at suppressing pest mite numbers than those collected in pasture. Shelterbelts with ground cover appear to harbour a diversity of beneficial organisms that suppress pest numbers in adjacent pastures.