Since the start of transformers immersed in refrigerating liquid, the fluid traditionally used has been mineral oil. However, in recent decades, efforts have been joined in the search for alternatives with a lower environmental impact and which also satisfy the technical requirements of insulation and refrigeration in the transformers. Currently, insulating vegetable oils are available in the market, which may have lower environmental impact during their use and final disposition; nevertheless, their high cost and short time of use have limited their massive application. This work presents the thermal behavior evaluation of two distribution transformers at different powers immersed in dielectric vegetable oil, comparing their performance with that of two constructively equal transformers immersed in mineral oil. The results obtained reveal that the transformers comply with the requirements of existing standards.