At the 2016 Summer Olympics in Rio de Janeiro, Brazil, Fratus arrived as one of the favorites to win a medal in the Men's 50 metre freestyle. He qualified for the final, but here, only finished in 6th place with a time of 21.79. In an interview, he said: "For some reason, I'm not able to swim faster than that. I have no idea what is happening. This year has been very bad. I have to review the program". Before the Games, Fratus was suffering from chronic back pain, and the Brazilian Aquatic Sports Confederation (CBDA) even sent a physiotherapist to the United States, where Fratus lives and trains to accompany the athlete.