Armenag Salmaslian was born on December 10, 1888, in Mkhalich, a village near Brusa (Bursa), in Turkey. He studied at the Berberian College in Constantinople between 1900 and 1906, followed by his studies at the Robert College (1906–1911).
He pursued higher education at the School of Law of the University of Paris and graduated in 1914. He published his book The Clause of the Most Favored Nation (1921, in French) and obtained a doctorate in jurisprudence in 1922.
Between 1920 and 1922, Salmaslian worked as a secretary of the Armenian National Delegation in Paris, and afterwards, he was private secretary to Nerses Khan Nersessian, honorary consul of Persia in the French capital until 1930.
After working for seven years at a law firm, Salmaslian became the head of the section of Oriental Languages at the National Library of France (1940-1947). In 1946 he published the first edition of his Armenian Bibliography. After the death of Aram Andonian, its founding director, in 1951 Salmaslian was designated director of the AGBU Nubar Library in Paris and held this position until 1967, when he was forced to leave because of health issues. He was a frequent contributor to the press on Armenian Studies. In the same year, he earned the Mesrop Mashtots medal of the Matenadaran of Yerevan. In 1969 he published a second expanded and revised edition of his Armenian Bibliography in the Armenian capital.
Salmaslian passed away in Paris on January 7, 1971.