After liberation the question of founding the National gallery is being got in the forefront within postwar euphoria relatively soon. The 1st congress of artistic and scientific workers founds the Artistic and Scientific Council which in year 1946 already obtained a task to negotiate the prepared programme of order on National Gallery by Authorization of Education and Enlightenment. Resolution of the 2nd Congress of Slovak artists and Scientists from October 28, 1946 urges on accelerated establishment of national gallery. Also a requirement to build up a new building for national gallery gets even into the draft of five year plan of cultural construction of Slovakia, elaborated by the Artistic and Scientific Council at the beginning of year 1948. The Central Action Committee of Slovak cultural workers requires again, among other things, also establishment of institution to which is given already definitive name of Slovak National Gallery.

Founding of the Slovak National Gallery has been confirmed by the Law of Slovak National Council No. 24 from the day July 29, 1948 which defines the gallery like state scientific, artistic and representative also folk- educational institute. By this the long-term efforts culminated and also the question of central state national gallery was solved-out. Above all Ladislav Novomeský the then Commissioner of Education and Culture was instrumental in its rise/origin to a distinct extent, similarly as well as for origin of further top cultural institutions.

The board of trustees has been charged by gallery administration by law and it had 6 members from spheres of specialists. Their composition has been defined also by law (1 sculptor, 1 painter, 2 art historians, 1 museologist and 1 architect of artistic direction).  The function of director has been offered to Karel Šourek regarding to his authorship of exhibition  Old art in Slovakia (Prague 1937), which meant breakthrough in viewing on the development of Slovak visual art from the oldest times up to the present day. In 1950 Šourek elaborated a conception of the Slovak National Gallery, however, for the sake of disease he could not already take this function.  After subsequent two-year intermezzo when Vladimír Novotný has been charged with leadership of the gallery as director of the National Gallery in Prague; in 1952 Karol Vaculík, art historian, takes over the function of director who played off an important role in further gallery direction. In complicated period of the fifties he prevented an implementation of considerations on the gallery like a detached workplace of Prague National Gallery, on fusion of the gallery with National Museum resp. and in spite of pressures and he managed to defend the autonomy of the institution. He had key role in founding, orientation and development of gallery´s collection funds but also in forming of its specialized, exposition and exhibition activities. The gallery´s activities are developed in a relevant way in relaxed atmosphere of the sixties; the gallery prepared many revealing projects. It implemented collected exhibitions of founders and classics of Slovak modern art, first monographs. It developed contacts in abroad and it brought also expositions of world-famous artists. The gallery participated in preparation of Venice Biennial and Sao Paulo Biennial. The normalization halted this promising enlivening at the end of the sixties (of past century).

In time of its origin the gallery obtained for its activity a three-wing (originally four-wing) Baroque building i.e. barracks of city police at the Danube riverbank so-called Water Barracks. In 1951 in these premises the first exhibition has been dedicated to Slovak visual art of 19th century and in 1955 after necessary adaptation also the first exposition “Art of 19th to 20th century (150 years of Slovak visual art expression)” arose. Relatively shortly after that the management came with requirement for extension of gallery premises. In 1963 an architectonic competition was carried-out and in years 1969 – 1977 a principal reconstruction and modern addition to historic object has run according to winning design of Vladimír Dedeček architect. However, the reconstructed gallery has been not opened by Karol Vaculík since in 1972 he has been dismissed of manager function. In 1975 for almost 15 years Štefan Mruškovič ethnographer undertook this post after short acting of J. Hraško and F. Gavula. Despite  normalizing and ideological acting, which has been reflected for example in purchases of ideologically engaged works, but also in exhibition programme often reflecting various political anniversaries the curators succeeded in carrying-through also of works of some authors taboo by regime into collections as study purchases. During its acting even though the gallery finished the reconstruction and gained vaster premises for presenting its collections in permanent expositions also for specialized background (restaurateur´s workshops, art and science library and the like), however, brave and generously outlined modern architecture has been ahead of technological possibilities and it suffered for maladies of socialistic civil engineering. More changes without consent of author and against its will have been carried-out in the project and process of construction. Moreover the project was not implemented as a whole one, it has been put into usage prematurely and in time of final inspection it had 1,200 defects.

After 1989 more managers were replaced in the gallery management. Zuzana  Bartošová as art historian left most distinct trace. During two years of her acting by intensive purchases she completed the collections with missing core works of the sixties up to the eighties and in exhibition activity she contributed to appreciation of work of more till then not being indicated, however, of key personalities of Slovak visual art scene. Organizationally she segmented the gallery into three components: Gallery of Modern and Old Art, Gallery of Contemporary Art and Gallery of Architecture, however, she received not enough time to crown this transformation. Juraj Žáry management/director returned to original model and to more traditional but more balanced exhibition programme. Because of undersized budget the acquisition activity was attenuated. After uninteresting acting of Pavol Muška artist, Katarína Bajcurová art historian took charge the gallery management in 1999, till then she was a specialized worker of SNG.