The Slovak National Gallery was established by the Slovak National Council by law (Act No. 24 of 29 July 1948). The opening exhibiton of the gallery was the Exhibition of Paintings of Old Masters from the SNG Collections(1949). The year of establishment of the gallery is relatively late when compared with other countries in Europe and it was the result of Slovak ambitions after the war, promoted mainly by Ladislav Novomeský, a poet, and then minister of education and culture. Historically, it was created as a traditional museum of Fine Arts of local as well as wider European provenance. The collection of artworks from the 20th century and mapping contemporary artistic culture were vital tasks of the Gallery from the beginning. In the course of its development, the collections were expanded to include other spheres of visual culture. The SNG enriched its activities by the acquisition of artefacts of Applied Art, Design, Photography, and Stage Design, and it explored the specific phenomenon of Naïve Art. Later, the collectors’ program expanded to include artefacts associated with the development of Architecture and Other Media. 
SNG's activities were initially focused on the acquisition, research, rescue, and presentation of cultural heritage, especially in all disciplines of art, painting, sculpture, drawing, and graphics, and gradually other areas of artistic creation have joined them. In 1960, the SNG's acquisition activity expanded into artworks of applied art and industrial art, and from 1965 to Naïve Art (obtained through international tours - Naïve Art Triennale); later it expanded in the field of scenography and artistic photography. Since 1986, the collections of architecture (studies, projects, models) have been profiled. The entire SNG collection consists of about 70,000 artworks, and interest is concentrated on the idea of ​​identifying with the history of Slovakia, with its cultural heritage. The focus lies on the field of art of Slovak provenance and art in Slovakia.
Today the SNG’s complex of buildings in Bratislava consists of the original structure of the Baroque Water Barracks, with an additional structure (the bridge and administrative building from the 1970s), and the Esterházy Palace (built in 1870).
Details about the operation of the gallery can be found in its Annual Report from 2016 available in Notes (only in the Slovak language).