The senior Congress leader was admitted to RML on Wednesday afternoon, sources said.
"He was brought to the hospital in the afternoon and is currently admitted. There is nothing to worry as it was a minor brain haemorrhage," said a doctor who asked not to be named.
The 76-year-old former Kerala Chief Minister also served as Defence Minister during the United Progressive Alliance government.
Doctors said that Mr Antony will remain in the hospital for two-three days after which he will be discharged.