For the protection of your own health, your family’s, as well as that of all those involved in offering you a safe hospitality, the following general principles regarding the health protocols apply in Greece as of the 19th of April:
Every traveler coming to Greece from abroad should have a negative PCR test from a diagnostic laboratory. The test has to be conducted no later than 72 hours before arrival. This test is mandatory for all tourists (including children over the age of 5), regardless of the epidemiological situation prevalent in the country of departure.
https://travel.gov.gr/#/