He introduced the method of the critical points at infinity, which is a fundamental step in the calculus of variations.
He attended the École Normale Superieure in Paris[1] in 1974, the first Tunisian to do so.
[1] His dissertation advisor was the French mathematician Haïm Brezis.
In October 1981, Bahri became a lecturer in mathematics at the University of Tunis.
[6] In 1989, Bahri won the Fermat Prize for Mathematics, jointly with Kenneth Alan Ribet, for his introduction of new methods in the calculus of variations.