He was a member and president of the Yugoslav section of the AICA (International Association of Art Critics).
As a critic of NIN from 1959 to 1963, his engagement in this field was especially emphasized when he clearly separated artistic from non-artistic phenomena.
He also made a significant contribution as a museologist, since he brought numerous innovations to the work of the National Museum in Belgrade and the Gallery of Contemporary Art in Niš, where he was the director.
Although the youngest director of this oldest museum institution in Serbia, Trifunović did not hesitate to introduce novelties that often met with strong resistance from the academic and artistic public.
Тхе Cultural Centre of Belgrade established the annual "Lazar Trifunović" Award in 1992.