Ousmane N'Doye was born on 21 March 1978 in Thiès, Senegal, starting to play junior level football at local club, ACS and he also practiced basketball until he was aged 12 or 13.
[6][15][18] Ousmane N'Doye was transferred from Académica to Romanian club Vaslui for €500.000, making his Liga I debut under coach Dorinel Munteanu on 23 February 2008 in a 3–0 home win over Dacia Mioveni, scoring his first goal in the competition on 15 March when he equalized in the 90th minute, after a counter-attack to obtain a 1–1 with Oțelul Galați.
[7][19][27] In 2009 he started to form a couple in the central midfield with Djakaridja Koné, the team reaching the Europa League group stage where N'Doye made four appearances, receiving a red card in a game with Galatasaray.
[19][29] In December 2010 Astra Ploiești bought him from Dinamo for €350.000, staying with the club one year in which he scored five goals in 26 league games, leaving afterwards free of contract to return at Vaslui where he was wanted by the coach he felt was like a father to him, Viorel Hizo, having previously working together in his first spell there.
[19][36] By the end of the season, N'Doye was the team's top-goalscorer, managing a career-best 12 goals in 23 matches, including three doubles against Ceahlăul Piatra Neamț, Botoșani and CFR Cluj, helping ASA fight for the title until the last round when they were defeated 2–1 by Oțelul Galați, thus finishing on the second place, on the first being Steaua.
[6][47][48] In the following years he played four games at the 2010 World Cup qualifiers, making his last appearance for the national team on 1 April 2009 in a friendly which ended 1–1 with Iran, having a total of 27 matches with one goal scored for the Lions of Teranga.
[7][39] During his years spent in Romania, thanks to his charisma and eccentric style, he would get very much media attention, offering funny moments in front of the camera like a conversation after a meeting on an airport with actor Florin Piersic.
[30][39][50][51] In April 2015, after a 1–0 away victory of ASA Târgu Mureș against Steaua București which helped his side reach the first position with five rounds before the end of the season, N'Doye said some ironies against his opponents in front of the cameras:"In one leg I beat them, I didn't practice after the match with CFR, until today.
[39][56] N'Doye was also a player who was not afraid of showing his emotions, as after Dinamo lost with 3–0 in front of Slovan Liberec in the first leg of the play-off for the group stage of the 2009–10 Europa League, he said in an interview:"If we can beat 4–0?
[59] His life outside the field gained very much attention in Romania, N'Doye being known for being late at team reunions, indiscipline moments, having conflicts with his teammates and also for liking to go out in clubs, including appearing on stage with rappers Puya and Akon.
[54][62] Also in 2010 he appeared in the "Be free" video of Smiley's band Radio Killer alongside former Romanian international footballer, Ioan Lupescu and former tennis ATP number 1, Ilie Năstase.