In 1925 Gillet moved to the United States to become principal oboist of the Boston Symphony Orchestra under conductor Serge Koussevitzky.
[2] Beginning September 1942, he joined the faculty at the New England Conservatory in Boston where he remained for over thirty years.
[3] For many years he also concurrently taught on the faculties at the Conservatoire de musique du Québec à Montréal and Boston University.
His notable pupils included Robert Freeman, Eugene Lacritz, Jean Northrup, Pierre Rolland, Raymond Toubman, and Allan Vogel.
[4] On Freeman's inauguration in 1973 as director of the Eastman School, Gillet was awarded an honorary DMA degree.