In his youth, Halys reached the final of the US Open in singles in 2014 , and in doubles that same year he won the French Open title alongside Benjamin Bonzi . He also won five singles titles on the Future Tour and three doubles on this one.
He celebrated his premiere at a Grand Slam tournament in 2015 at the French Open , where he was defeated by Rafael Nadal in three sets. Last week he moved into a main field of an ATP tournament in Nice for the first time .
In May 2016 he won his first Challenger tournament in singles. He won against Frances Tiafoe in Tallahassee 6: 7 6 , 6: 4, 6: 2.