The final settlement of the borders of the Balkan states after the termination of the Second Balkan War occurred with the Treaty of Bucharest.

After the armistice, negotiations, in which the Great Powers participated, began in the Rumanian capital. The issues between Bulgaria and Serbia were easily resolved. The basic points of friction in the negotiations were between Greece and Bulgaria and concerned the latter's access to the Aegean. More specifically, the fate of the port of Kavala and generally of eastern Macedonia were at stake. Thanks to the attitude of the Great Powers and the conjunction of circumstances the Conference provided, the Greece claimed the banks of the River Nestos as its eastern border.

On 28 July/10 August 1913 the definitive peace treaty between the belligerents was signed. The Greco-Bulgarian border was fixed on the Serbian-Bulgarian borders in Beles mountain and reached as far as the coasts of the Aegean, at the mouth of River Nestos. Eastern Macedonia, Kavala, Serres and Drama, central and western Macedonia up to Florina and Prespes were accorded to Greece. Western Thrace was ceded to Bulgaria, whereas eastern Thrace from Ainos to Didymoteichon remained in Turkey.

The Treaty of Bucharest was of great importance for Greece. The surface area of the hitherto small state doubled, increasing from 63,211 to 120,308 square kilometres, and so did its population, which rose from 2,631,952 to 4,718,221 inhabitants. This development reinforced both the economic growth and the position of the country in the context of international relations. But not all contested areas were gained, in fact many of them remained under Bulgarian or Turkish control, and there was no clear regulation concerning the status of northern Epirus and the islands.