In northeast Spain, the most common predators found in tomato fields and greenhouses are the mirids Macrolophus caliginosus Wagner and Dicyphus tamaninii Wagner. Natural colonization occurs during the growing season and both species prey on whiteflies. Because D. tamaninii can damage tomato fruits during periods of prey scarcity, a semifield experiment was carried out to evaluate whether the presence of M. caliginosus affects damage produced by D. tamaninii. In a tomato greenhouse, 60 plants were individually caged and distinct predator treatments were introduced: D. tamaninii, D. tamaninii eggs of Ephestia kuehniella Zeller, D. tamaninii M. caliginosus, M. caliginosus alone, and a control without any insect. Damage to tomato fruits was recorded (>25% of the fruit) in all the treatments with D. tamaninii, whereas no significant damage was detected with M. caliginosus alone. Finally, no intraguild predation was detected between both mirid species.