Meillet completed his doctorate - Research on the Use of the Genitive-Accusative in Old Slavonic in 1897. In 1902 he took a chair in Armenian at the École des Langues Orientales. In 1905 he was elected to the College de France, where he taught on the history and structure of Indo-European languages. He worked closely with noted linguists Paul Pelliot and Robert Gauthiot.
Today Meillet is remembered as the mentor of an entire generation of linguists and philologists who would become central to French linguistics in the twentieth century, such as Émile Benveniste, Georges Dumézil, and André Martinet.
At the Sorbonne, beginning in 1924, Meillet supervised Milman Parry. In 1923, a year before Milman Parry began his studies with Meillet, Meillet wrote the following (which, in the first of his two French theses, Parry quotes):
Homeric epic is entirely composed of formulae handed down from poet to poet. An examination of any passage will quickly reveal that it is made up of lines and fragments of lines which are reproduced word for word in one or several other passages. Even those lines of which the parts happen not to recur in any other passage have the same formulaic character, and it is doubtless pure chance that they are not attested elsewhere.Meillet offered the opinion that this pattern (the so-called Oral Formulaic Hypothesis) might be a distinctive feature of orally transmitted epics (which the Iliad was said to be). He suggested to Parry that he observe the mechanics of a living oral tradition to confirm whether this suggestion was valid; he also introduced Parry to the Slovene scholar Matija Murko, who had written extensively about the heroic epic tradition in Serbo-Croat and particularly in Bosnia with the help of phonograph recordings. From Parry's resulting research in Bosnia, the records of which are now housed at Harvard University, he and his student Albert Lord revolutionized Homeric studies.
Meillet supported the use of an international auxiliary language. In his book The Search for the Perfect Language, Umberto Eco cites Meillet as saying, "Any kind of theoretical discussion is useless, Esperanto is functioning". In addition, Meillet was a consultant with the International Auxiliary Language Association, which presented Interlingua in 1951.