The agent, a man with 19 years’ experience in the service, was in Scotland working on presidential protection when he fell ill on Sunday.
He had been receiving “critical care” from medics in Scotland but died on Tuesday morning, surrounded by members of his immediate family.
The US secret service confirmed the death “with great sadness and regret” in a statement and described the man as a “dedicated professional of the highest order”.
It added: “The secret service thanks the medical personnel in Scotland, in addition to the members of the White House Medical Unit and Police Scotland who provided exceptional care and support for a member of our family.”
The service has not released the man’s name to give his family privacy and time to inform others.
President Trump left Turnberry on Sunday, flying out of Prestwick Airport to Helsinki, Finland, for talks with Russian president Vladimir Putin on Monday.