The Brazilian playmaker returned to his boyhood club, Sao Paulo, in December 2024, but has now been forced to hang up his boots.
Oscar suffered a serious heart scare during a training session with the club during pre-season, losing consciousness while on a stationary bike.
Sao Paulo have now released a video of Oscar speaking about the gravity of the situation, in which he said: "My heart stopped for two minutes, two and a half minutes.
“I took the test, ended up fainting, my blood pressure kept dropping, and my heart was stopping. They performed cardiac massage. I only remember fainting."
"It's difficult because I wanted to do more for Sao Paulo; I wanted to play more.
“I had the football in me and the right age, and I could have kept going, but unfortunately, this happened. Now I will retire and continue as a supporter. I'll move on with my life as a fan."