The Third National Assembly took place under different conditions than the two previous ones. The civil conflicts of 1824 had terminated, without however solving the organizational weaknesses of the central administration, while the persecutions of the defeated continued even when Ibrahim had landed in the Peloponnese (beginning of 1825). The preparations for the organization of a National Assembly which had begun in September 1825 did not advance in these conditions. Conversely, the rival factions were reorganized, creating renewed tension. Finally, the Third National Assembly opened its proceedings on 6 April 1826 at Piada, but was soon interrupted because of the fall of Missolongi. In the meantime it was decided that the Greeks had to appeal to Great Britain to intervene and determine the terms of the negotiation, while a new administration, called the Administrative Committee, was formed. In autumn of the same year (1826) attempts were made to call another National Assembly, but without success. Conversely, small-scale civil conflicts broke out in Corinthia and Nauplion while at the beginning of 1827 the rival factions organized separate assemblies at Aegina and Ermioni. Finally the assemblies were united at Troizina at the end of March 1827, thus expressing the wish of both sides to achieve a common political agreement. The Third National Assembly was completed at the beginning of May with two important decisions.

The first involved the voting of a new constitution which would no longer be provisional. Among other provisions, the Political Constitution of Greece redefined the terms of negotiation with the Ottoman Empire seeking independence and not autonomy. Finally, the creation of a one-member administrative organ which would be at the head of the executive power was decided upon. Thus, the office of the Governor was instituted. Ioannis Kapodistrias was chosen for this position with a seven-year term of office. In August of the same year (1827) Kapodistrias accepted the proposition of the National Assembly. Until his arrival a special cice-governmental Committee would assume his duties as it was formed for this purpose.

Kapodistrias managed quickly to suspend the Constitution of Troizina, which had been formed in such a way as to restrict his power and control his acts. In the place of the Parliament a new organ was created, the Panellinio, which was only of a consultative character. About one and a half year after the appointment of Kapodistrias the Fourth National Assembly (Argos, 11 July-6 August 1829) ratified the powers concentrated in the hands of the Governor. In addition, instead of the Panellinio, which was abolished, a Senate with fewer members and which lacked ultimate authority, was formed. Finally, the fundamental principles of a future constitutional revision were defined. Such a thing never came about. The sharpening of political opposition and the assassination of Kapodistrias during the preparations for the organization of the Fifth National Assembly led to a new round of civil conflicts. In fact, the two groups proceeded to organize two separate national assemblies, the acts of which had no importance other than that of supporting the two sides during the conflicts.