Researchers assessed yields of sunflower/soybean intercrops in the Southern Pampas (Argentina), and evaluated the composition, richness, and abundance of weeds and insects. Sunflower/soybean sole crops and intercrops were sown during two consecutive years. Yield advantage of intercropping was indicated by land equivalent ratios higher than 1, indicating that intercrops were more productive than sole crops. Weed and insect species were more diverse in intercrops than in sole crops, though actual numbers were similar. Intercropping warm-season crops can therefore promote biodiversity and yield in conventional cropping systems in temperate regions.