He made his debut as a professional boxer on 6 March 2009 against Travis Dickinson and lost on points. He was also the youngest fighter ever to take part in the competition at the age of 19. Mendy fought his first professional fight on 6 March 2009 and had a bad start to his career losing his first two fights against debuters Travis Dickinson and Tobias Webb.
On June 30, 2010, Mendy competed in the 13th series of and came out the eventual winner of the competition. He came in to the competition following a loss from undefeated Kenny Anderson. In his first fight he beat Sam Horton by TKO in the 1st round and broke the record for the fastest ever knockout in at 82 seconds (1:22min). In the semi-final he beat Daniel Cadman by unanimous decision with all the scorecards reading 29-28 in favour of Mendy. In the final he fought in form Paul David and won on unanimous decision again and received £32,000 for his win, the judges scorecards were all in favour of Mendy, 29-28, 29-28, 30-27. In this series he broke an outstanding 3 records: Youngest ever contestant (19 years and 276 days) Youngest ever winner (19 years and 276 days) Fastest ever knockout (Vs Sam Horton in 82 seconds (1:22) I believed in myself and I said at the beginning I would win this - there were no doubts about it On 22 November 2014, Mendy fought against Polish boxer Robert Swierzbinski in Białystok, Poland. Mendy won by unanimous decision and received a first professional belt in his career - WBF in middleweight division. 2010 - 13 (super-middleweights) champion.
