As part of Mr Gross’s work, he imported satellite equipment that was deemed illegal.
The Cuban authorities said his activities were an attempt at a regime change, and sentenced him to 15 years for committing "acts against the integrity of the state".
Washington always protested his innocence. Obama administration officials have considered Mr Gross's imprisonment an impediment to improving relations with Cuba.
Last week, Mr Obama said the US had been “in conversations” with Cuba about Mr Gross for some time.
Mr Gross is believed to have suffered from ill health, including arthritis and weight loss, during his imprisonment.
In August, he said he could no longer take life in prison and was thought to have said goodbye to his family.
Mr Obama said: “We think that he shouldn’t have been held in the first place.”
