The objective of this work was to evaluate the effect of different grain sizes and treatments in the physiological quality of seeds and performance of soybean cultures. The object of analysis were seeds from the cultivars Monsoy 5730 IPRO and Monsoy 5947 IPRO, sized 5.5 and 6.5 mm. The industrial seed treatment was carried out in lot equipment, with the products cyantraniliprole, thiamethoxam, metalaxyl, thiabendazole, and a combination of fludioxonil + polymer + talc. The conventional treatment was performed with the products cyantraniliprole, thiamethoxam, metalaxyl, thiabendazole, and fludioxonil. Part of the seeds was kept untreated (control). The experiment used a randomized block design, with four replications. The parameters assessed include the moisture content measurement, seed coating, germination, first germination count, field emergence, survival rate, and grain yield (right after the seed treatment and after 45 days of storage). The industrial treatment method produced a better seed coating. As for seed size, it had no effect on quality or grain yield. Last, the treated seeds presented the best results for emergence in field, while the industrial treatment achieved the highest productivity.