Stanley Johnson posted videos on Instagram taken from a plane with the words “Arriving in Athens this evening!” as well as a photo of himself in a mask in what appeared to be an airport.
The elder Johnson, 79, has a villa in Greece.
Greece has banned flights from the UK until at least July 15.
The Daily Mail reported that Stanley Johnson flew to Athens via Bulgaria.
He told the newspaper he was visiting Greece on “essential business trying to COVID-proof my property.”
Opposition politicians accused the prime minister’s father of flouting lockdown rules.