The Balkan Sprachbund is a well-known linguistic area largely identifiable with the Balkans, which has over the centuries been the stage of complex historico-political and social events resulting in situations of bi- or multilingualism. Consequently, Balkan languages, including Mod. Gk., share striking structural convergences – so-called ‘Balkanisms’ – even though each language retains its own identity. While the origins of phenomena considered Balkanisms often go far back in time, actual convergences between Balkan languages did not begin to appear until the Medieval period, and only later reached their current form. Given the complexity of the development of Balkanisms and their relatively late occurrence in the history of Gk., this article provides only a brief overview of the Balkan Sprachbund and related issues. It reviews the early evidence of those phenomena that later became Balkanisms, taking into consideration Gk. language data up to the Medieval period and, where necessary, up to the present day.