He was member of the Serbian Academy of Sciences and Arts.
Ferjančić was born in Belgrade, at the time part of the Kingdom of Yugoslavia.
Ferjančić graduated with distinction from the Faculty of Philosophy at the University of Belgrade in History in 1953 and after additional study at the same university, he received his doctorate in 1960[2] with a dissertation entitled Despots in Byzantium and the Lands of the South Slavs.
[2] In 1973 he assumed the chairmanship of the Institute for Byzantine Studies after George Ostrogorsky's retirement, a post Ferjančić occupied until his death in 1998.
In 1977 he became the director of the institute, a post held by Ostrogorsky before he died in 1976.