The aim of this study was to evaluate the effect of the herbicide atrazine, recommended for weed control in corn, on 10 species of Trichogrammatidae (Hymenoptera). A female of each trichogrammatid was placed individually in a test tube (no-choice) with a card containing approximately 45 Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) eggs. Parasitism by these trichogrammatids was allowed for 48 h, and the cards were sprayed with the herbicide atrazine at 6 L/ha, along with a control (distilled water). Atrazine reduced the emergence of Trichogramma bruni Nagaraja females, but increased that of Trichogramma pretiosum Riley, Trichogramma demoraesi Nagaraja, Trichogramma galloi Zucchi, and Trichogramma soaresi Nagaraja. In addition, atrazine reduced the sex ratio of T. bruni, Trichogramma atopovirilia Oatman & Platner, and Trichogramma bennetti Nagaraja & Nagarkatti, and increased that of T. demoraesi and T. soaresi. The herbicide was slightly harmful to T. bennetti and T. bruni, but was relatively harmless to the other species of Trichogrammatidae based on the standards of the International Organization for Biological Control (IOBC).