In December 1972, the archaeologist and art historian Dimitris Papastamos (1923-2008) took over the direction of the National Gallery, remaining in this position until October 1989.

During Dimitris Papastamos’s tenure, the National Gallery was firmly consolidated, the result of the final resolution of the question of housing and a radical administrative overhaul.

In 1976, the second part of the building complex was completed. The National Gallery was officially inaugurated on 17 May 1976 by the President of the Hellenic Republic, Konstantinos Tsatsos, and Prime Minister Konstantinos Karamanlis.

In 1980, Law 1079 was passed, which regulated the structure and operation of the National Gallery – Alexandros Soutsos Museum. This law abolished most of the provisions of Law 2814/1954 and instituted new activities, enabling the collections to be expanded and the museum departments to be reorganised and developed in line with modern requirements.

Thus, the National Gallery agencies were set up as a Directorate General with three Directorates: i. Collections, Artistic and Museological Programming, ii. Administrative-Accounting, and iii. Art Conservation and Restoration. Staff growth was spectacular and covered all the requisite specialties, while the curation of the collections was for the first time assigned to art historians, who also catered to their systematic organisation.

The collections were enriched, alongside substantial donations of artworks by artists including Tassos, Nikolaos Ventouras, Giorgos Moschos, Konstantinos Parthenis, Umvertos Argyros, Giorgos Gounaropoulos, Nikos Hadjikyriakos-Ghika and Yannis Moralis. Also, Eugène Delacroix’ Greek Fighter on Horseback was acquired, thanks to the support of Stavros Niarchos and Vassilis Goulandris; the large-scale fresco by Fotis Kontoglou installed in the artist’s home was acquired with support from Vassilis and Nikos Goulandris; and Rodin’s The Prodigal Son was acquired with funds from Odysseas Fokas’ bequest as well as a financial contribution by Vassilis Goulandris.

The resolution of the housing issue enabled the permanent display of the collections, which since 1977 included works from the Evripidis Koutlidis collection. Moreover, extensive and systematic exhibition activity was developed, with added emphasis on the promotion of Greek artists’ work. There were also exhibitions by foreign artists, many of which took place in the context of transnational exchanges, as well as some outstanding group exhibitions. Exhibitions were also organised in other countries as well as all around Greece, aiming at promoting visual arts education, especially among school children. A variety of art events, lectures, conferences, theatrical performances of children's plays and puppet theatre were also organised, and a children's workshop was set up.

In 1983, the Coumantaros Art Gallery was established in Sparti, becoming the first National Gallery Annexe.

Finally, with the financial contribution of the painter and engraver Koula Bekiari-Vekri, the first Glyptotheque was established in 1986 in independent premises in the museum and remained in operation until the early 1990s. This was the first independent permanent display of the National Gallery’s collection of sculpture and traced the evolution of Modern-Greek sculpture until 1940.