Diomandé came out of the Jean-Marc Guillou academy in Abidjan, before joining the Guidars FC, in Mali. He moved to Olympique Lyonnais in September 2019 for a fee of €550,000, with bonuses rising up to €2 million.[3][4]
After a year of playing in Lyon's reserve team, where he became one of the players most used by Gueïda Fofana, and an impressive summer preparation, Diomande made his professional debut for Olympique Lyonnais on 18 September 2020, helping his team keep a clean sheet against Nîmes in this Ligue 1 encounter.[5][6]
On 30 August 2024, Diomandé was transferred to Auxerre, signing a three-year contract.[7]