The Diff'rent Strokes star, who found fame at 11, was just 42.
He was taken to the Utah Valley Regional Medical Center in Provo, Utah, after suffering a brain haemorrhage at home on Wednesday. The injury is believed have been caused by a fall.
Gary played Arnold Jackson in US TV series Diff'rent Strokes from 1978 to 1986 and is estimated to have earned - and lost - a £12 million fortune.
Gary filed for bankruptcy in 1999 and ended up working as a security guard.
Standing just 4ft 8in tall, he suffered from kidney condition nephritis and had two kidney transplants before the age of 14.
Gary's health had not been good in recent months and in January and February he suffered seizures.
'Thanks to everyone for their well wishing and support during this tragic time,' says Gary's manager.
'Gary is now at peace and his memory will be kept in the hearts of those who were entertained by him throughout the years.'
