- January 2: An earthquake registering 5.2 on the Richter scale strikes Kefalonia.
- January 5: Greek boxer, Anton Christoforidis, marks his US debut by defeating Willie Pavlovich in Madison Square Garden, New York.
- January 26: Greece and Britain sign a major trade agreement.
- June 2: Panathinaikos defeat Aris 3-1 at the Leoforos Stadium and lift the Greek Football Cup for the first time. The match is played during wartime, on the eve of the allies’ evacuation of Dunkirk.
- July 8: The Olympic Swimming Complex, constructed under the initiative of the Hellenic Olympic Committee at a cost of 7.5 million drachmas, is inaugurated.
- July 12: Two Greek Navy auxiliary vessels - the Orion and the Hydra - are attacked by Italian aircraft off the coast of Crete.
- October 28: Prime Minister Ioannis Metaxas replied with the single-word reply "no", when Mussolini demanded occupation rights to strategic Greek sites. Greece officially entered World War II.
- October 30: Pilot Officer Evangelos Yiannaris becomes the first Greek officer to be killed during World War II.
- October 31: Greek warships "Psara" and "Spetses" bombard Italian positions in Albania.
- October 31: British forces land in Crete.
- November 1: Lieutenant Alexandros Diakos becomes the first Greek Army officer to die in World War II.
- November 2: The Italian Air Force bombs Ioannina causing civilian casualties.
- November 3: The first Greek units cross the Albanian border in pursuit of the Italian army.
- November 9: After the complete failure of the invasion of Greece by the Italian military, Mussolini replaces General Sebastiano Visconti Prasca with General Ubaldo Soddu, his former Vice-Minister of War.
- November 17: The last Italian invaders leave the Greek soil.
- November 18: German leader Adolf Hitler and Italian Foreign Minister Galeazzo Ciano meet to discuss Benito Mussolini's disastrous invasion of Greece.
- November 22: The Greek army on the counter-offensive enters Korytsa in World War II
- November 24: The Greek army "liberates" the town of Moschopolis (known in Albanian as Voskopoja and in Aromanian as Moscopole) of Northern Epirus (Albania) during the counter-offensive operations against the Italians in WWII
- November 27: The Battle of Pogradec commences.
- November 30: The Greek Army enters Pogradec.
- December 3: The Greek army liberates Premeti.
- December 5: Colonel Mardochaios Frizis (Μαρδοχαίος Φριζής) is killed near Premeti during the Greek-Italian confrontation. He is the first high ranking officer to fall in battle in World War II.
- December 6: The Greek army liberates Agioi Saranda.
- December 8: The Greek army liberates Argyrokastro.
- December 17: Dr. Vasilios Vergis, on his own initiative, lands with a band of 14 men on Agathonisi and captures its Italian garrison as prisoners.
- December 22: The Greek army liberates Chimara.
- December 22: The Submarine Papanikolis, under the command of Lt.Cdr. Miltiades Iatridis, sinks the Italian sailing vessel Antonietta by ramming in the Adriatic.
- December 24: Submarine RHS Papanikolis, under Lt.Cdr. Miltiades Iatridis, torpedoes and sinks the Italian merchant ship Firenze (3952 BRT) in the Adriatic, off Saseno Island
- December 29: As the situation on the Albanian Front gets worse for the Italian forces, Mussolini replaces General Ubaldo Soddu with General Ugo Cavallero.
- December 29: Submarine RHS Proteus, under Lt.Cdr. Michail Hadjikonstantis, sinks the Italian merchant ship Sardegna in the Adriatic but is sunk itself by Italian war ships.
- December 31: Submarine RHS Katsonis, under Lt.Cdr. Athanasios Spanidis, sinks the Italian merchant ship Quinto in the Adriatic
- November 1: Lt Alexandros Diakos, first Greek officer to fall in battle in WWII
- November 17: Giorgos Vatikis, footballer - killed in action.
- November 18: Dimitris Pierrakos, footballer killed in the Battle of Pogradec