Yahya Jammeh stole the money from state coffers before leaving for exile in Equatorial Guinea, justice minister says.
The decision announced on Monday comes almost two years after Jammeh was forced into exile in Equatorial Guinea after he refused to concede defeat in a presidential election.
Jammeh ruled the tiny West African country for two decades. He lost a democratic election to Adama Barrow in December 2016.
However, Jammeh refused to step down, which prompted a military threat by the African Union and the West African regional body ECOWAS. He fled to Equatorial Guinea in January 2017.
The State Department said Jammeh is now being banned entry to the country under a category that applies to foreign government officials who are believed to have committed “significant corruption or a gross violation of human rights”.
In addition to Jammeh, his wife Zineb, and their daughter Mariam and son Muhammad are also being blocked.
The Barrow government reported that Jammeh stole at least $50m from the country while in office.
Jammeh, who attended a military training course in Alabama, owns real estate in Potomac, Maryland, about 24km from Washington, DC.
An estate previously owned by former American basketball player Calbert Cheaney, it was sold to the Jammeh family trust in 2010 for $3.5m, according to public records.