His substantial private collection is now in the hands of various institutions, while his written body of work helped lay the foundation for art history to become a serious discipline in his country.

That autumn, following Ionnescu-Gion's proposal, he was named a teacher at Matei Basarab, which allowed him to finance his studies at the Literature and Philosophy Faculty of the University of Bucharest.

He declared his support for the 1907 Romanian Peasants' Revolt, and in January 1917, during World War I, after he had condemned the German occupation authorities, he was among sixty intellectuals and bureaucrats who were arrested in Turnu Severin.

[3] While attending specialized courses in France, he became close friends with Henri Focillon, whose biography he later wrote, and whose letters to Oprescu were published posthumously.

Although a pragmatic collaborator with the regime, he nevertheless hired marginalized or persecuted figures such as Ion Frunzetti, Alexandru Paleologu, Remus Niculescu, Emil Lăzărescu, P. H. Stahl and Pavel Chihaia.

[1] In 1961, he became one of a select group of individuals to have received the Communist state's second-highest honor, the Order of the Star of the Romanian People's Republic, first class.

[7] During his time at the institute, he promoted scientific research, archival and field work, and its endowment with books and documents that would later develop into a library.

[1] At first focused on peasant art and on painters including Gheorghe Petrașcu and Ion Andreescu, in 1937 he published Pictura românească în secolul al XIX-lea ("Romanian Painting in the 19th Century"), the first integral account of the topic.

[1] He published numerous studies and articles in domestic and foreign art history magazines, with the following popular publications also hosting his work: Contemporanul (1951–1969), Flacăra (1954–1969), Luceafărul (1956–1966), Ramuri (1964–1969), Revista Fundațiilor Regale (1944–1946), La Roumanie d'aujourd'hui (1963–1966), La Roumanie nouvelle (1954–1958), Scînteia (1954–1969), Scînteia Tineretului (1963–1968), Universul (1932–1947) and Viața Românească (1937–1940).

In early 1959, he was summoned by police investigators looking into homosexual activity by a number of individuals, among them Oprescu's employee, the musicologist Mihai Rădulescu and the latter's lover, the documentary filmmaker Petre Sirin.