Fabrisio Saïdy was born in Madagascar. When he was four years old, he lived on Réunion . He took part in the French youth championships for the first time in 2015 and was able to take sixth place over 400 meters in the U18 championships. A year later he won silver over 200 meters at the same championships. In 2017 he moved up to the higher age group and was able to at least take part in the U20 European Championships in Grosseto with the relay , with which he won the silver medal. In 2018 he also started the 4 x 400 meter relay at the U20 World Championships in Tampere, where the quartet took fourth place. In his favorite discipline, the 400 meters, he also stayed under 47 seconds for the first time in 2018.
In March 2019, Saïdy won bronze in the relay at the European Indoor Championships in Glasgow. In the individual competition, he finished fifth in 46.80 seconds. In May, the French 4 x 400 meter relay finished second in the B final at the IAAF World Relays , making it 10th overall. In July he went to the U23 European Championships in Gävle, Sweden, where he won the gold medal in a personal best of 45.79 s. With the relay he also won another bronze medal.