Several studies have been carried out to obtain unsaturated fatty acid (UFA) concentrates, due to their nutritional importance in food applications. The aim of this work was to obtain UFA concentrates from bleached cobia (Rachycentron canadum) and Argentine croaker (Umbine canosai) oil by complexation with urea, and to evaluate their physicochemical and thermal properties during processing. The fatty acids found in high amounts in the crude and bleached oils of cobia and Argentine crocker were palmitic, oleic and linoleic acids. Higher percentages of UFA were present in the oils extracted from the visceras, around 69 and 63% for cobia and Argentine croaker, respectively, and after complexation with urea, the percentages of UFA present in both concentrates were around 88%. Through the thermograms it was possible to observe that the UFA concentrates showed a 50% decrease in their maximum degradation temperature.