Kosmas was born in the Greek village of Mega Dendron near the town of Thermo in the region of Aetolia.

[5] He called upon Christians to establish schools and learn Biblical Koine Greek, so that they might understand the Scriptures better and generally educate themselves.

[6] Kosmas was also viewed with suspicion by officials of the Venetian Republic, then in its final stages of decline, which ruled parts of the territory where he was active.

Nevertheless, in one of his preachings he stated specifically that: "Those who wrong Christians, Jews or Turks (could refer to Muslims in general) would be paid back for the injustice they committed".

[citation needed] Kosmas held highly negative views on the use of the Aromanian and Albanian (Arvanitika more precisely) languages.

[8] One effect of his preaching was to transfer the holding of the weekly bazaar (fair) from Sunday to Saturday, which brought economic losses to Jews – barred by their religion from engaging in business on Sabbath.

There were no formal charges brought against him, nor was he put on trial before being executed – leading to various theories, persisting up to the present, about who might have wanted him dead.

[11][9][10] Although a hellenizer, Saint Kosmas the Aetolian is still highly regarded by Orthodox Albanians for the message that he gave.