This flag was based on their coat of arms, whose pattern is supposed to be derived from the standards of their claimed ancestor, Byzantine Emperor Nicephorus II Phocas (963–969 AD).

This pattern (according to not easily verifiable descriptions) included nine stripes of alternating blue and white, as well as a cross, assumed to be placed on the upper left.

In the surviving pictorial sources of the middle and later Empire, primarily the illustrated Skylitzes Chronicle, the predominating colours are red and blue in horizontal stripes, with a cross often placed in the centre of the flag.

[6] There is no mention of any "state" flag until the mid-14th century, when a Spanish atlas, the Conosçimiento de todos los reynos depicts the flag of "the Empire of Constantinople" combining the red-on-white Cross of St George with the "tetragrammatic cross" of the ruling house of the Palaiologoi, featuring the four betas or pyrekvola ("fire-steels") on the flag quarters representing the imperial motto Βασιλεύς Βασιλέων Βασιλεύων Βασιλευόντων ("King of Kings Reigning over those who Rule").

The (quartered) arrangement that includes the Cross of St. George is documented only in the Spanish atlas, and most probably combines the arms of Genoa (which had occupied Galata) with those of the Byzantine Empire, and was most probably flown only in Constantinople.

[8] Pseudo-Kodinos records the use of the "tetragrammatic cross" on the banner (phlamoulon) borne by imperial naval vessels, while the megas doux displayed an image of the emperor on horseback.

[9] During the Ottoman rule several unofficial flags were used by Greeks, usually employing the Byzantine double-headed eagle (see below), the cross, depictions of saints and various mottoes.

The first flag featuring the design eventually adopted was created and hoisted in the Evangelistria monastery in Skiathos in 1807.

Several prominent military leaders (including Theodoros Kolokotronis and Andreas Miaoulis) had gathered there for consultation concerning an uprising, and they were sworn to this flag by the local bishop.

[10] European monarchies, aligned in the so-called "Concert of Europe", were suspicious towards national or social revolutionary movements such as the Etaireia.

The First Greek National Assembly, convening in January 1822, thus took steps to disassociate itself from the Etaireia's legacy and portray nascent Greece as a "conventional", ordered nation-state.

[10] On 7 February 1828 the Greek flag was internationally recognised for the first time by receiving an official salutation from British, French, and Russian forces in Nafplio, then the capital of Greece.

[11] After the establishment of the Kingdom of Greece in 1832, the new king, Otto, added the royal coat of arms (a shield in his ancestral Bavarian pattern topped by a crown) in the centre of the cross for military flags (both land and sea versions).

Usages cited include the pattern of blue and white formations included on the shield of Achilles,[19][8] the apparent connection of blue with goddess Athena, some of Alexander the Great's army banners,[3] possible blue and white flags used during Byzantine times,[19][8] supposed coats of arms of imperial dynasties and noble families, uniforms, emperors' clothes, patriarchs' thrones etc.,[3][20] 15th century versions of the Byzantine Imperial Emblems [8] and, of course, cases of usage during the Ottoman rule and the Greek revolution.

Although it implies the use of a light shade of blue, such as on the flag of the United Nations, the colours of the Greek flag tend to be darker, especially during the dictatorship and in recent years, with the exception of the years of the rule of King Otto, when a very light shade of blue was used.

[22] Although 17 November is not an official national holiday, Presidential Decree 201/1998 states that respects are to be paid to the flag on that particular day.

[28] The war flag (equivalent to regimental colours) of the Army and the Air Force is of square shape, with a white cross on blue background.

[30] Since the Fire Service and the Hellenic Police are considered civilian agencies, they are not assigned war flags.