[2] After appearing as an unused substitute on five occasions,[3] Dembélé finally made his Stade Rennais, starting the whole game, in a 1–1 draw against Metz on 26 January 2008.

In summer of 2009, Dembélé was loaned to Boulogne, recently promoted to Ligue 1, to gather some professional experience.

[13] Dembélé was sent-off in the second-half on his league debut on 23 August 2011, in a 3–1 loss against Le Mans.

[14] However, Dembélé failed to make a first team his and his time there included a brief loan to Red Star in January 2012.

[18] Upon joining Stevenage, manager Graham Westley commented about Dembélé's talent, stating he "got a lot of quality; he's quick, very strong in the air and he can play the game.

"[26] However, he struggled to regain his left-back position in the first team, due to Darius Charles being preferred and his own injury concerns.

[29] In his last appearance for Stevenage against Southend United in the play-offs, Dembélé was involved in a collision with Michael Timlin, leading him to miss out in the second-leg.

[34] Dembélé made his Barnet debut in the opening game of the season, starting the whole match, in a 2–0 defeat against Leyton Orient.

[36] Dembélé then scored his first goal for the club, in a 2–1 loss against Wolverhampton Wanderers in the second round of the League Cup on 25 August 2015.

[50] By the end of 2016, he scored three more goals later in the 2016–17 season against Plymouth Argyle,[51] Newport County[52] and Luton Town.

[53] Dembélé also captained Barnet for the first time, in a 2–1 loss against Peterborough United in the EFL Trophy.