The attacking midfielder spent five days in hospital after being diagnosed with vasovagal syncope, a condition caused by a sudden drop in blood pressure, heart rate, and cerebral blood flow. Oscar, who had a contract with São Paulo that was due to expire in 2027, confirmed the decision on Saturday.
The 34-year-old, who won two league titles in five years at Chelsea, has not played since the incident in November. His retirement brings an end to a professional career that saw him represent Brazil internationally.