He died of cancer on 12 March at a prison medical centre in Springfield, Missouri, his daughter Amanda Myers Klein said.
Myers was serving a life sentence for conspiracy to commit espionage and wire fraud after passing sensitive US intelligence to Cuba for about 30 years.
His wife and fellow spy, Gwendolyn Myers, died in 2015 after serving an 81-month sentence; the couple also forfeited $1.7 million in assets.
How many more 'long game' Cuban spies remain undiscovered inside the U.S. government?
If old spies used radios, what methods are modern agents using to evade detection today?
What was the true extent of the damage caused by decades of undetected Cuban espionage?