[9][10][11] NKoulou also played in the Coupe de France Final, coming on as a substitute for Eduardo Costa in the 111th minute, in a 1–0 loss against PSG[12] and went on to make 23 appearances in the 2009–10 season despite being committed to the African Cup of Nation.

[14] Nkoulou continued remain in the first team, playing in the defensive midfielder position for most of the season and central defence.

English club Arsenal,[18] Spanish sides Sevilla and Atlético Madrid[19] and French champions Olympique Lyonnais have all declared their interests in the Cameroonian defender.

[22] After missing two matches, due to suspension he received while at Monaco,[23] Nkoulou made his Marseille debut on 14 August 2011, in a 2–2 draw against Auxerre.

[28] Nkolou continued to remain in the first team for the 2011–12 season despite another suspension (which he got a two match ban against Dijon[29]) and a knee injury.

[36] Nkoulou was ever–present in the 2012–13 season, having played all the match in the league and scored his first goal for the club, in a 2–1 win against Troyes on 3 March 2013.

[37] During the season, Nkoulou suffered a knee ligament injury and was sidelined for weeks, but managed to return to the league.

[38] At the end of the 2012–13 season, Nkoulou was named Trophées UNFP du football's Team of the Year of 2013 for the second time running.

[39] Prior to the 2013–14 season, Nkoulou stated he was prepared to leave Marseille in the summer,[40] prompting attracted interests from his former club Monaco,[41] who were just promoted back to Ligue 1, and Arsenal.

[57] After two months without playing, Nkoulou made his first team return on 12 April 2015, in a 1–0 loss against Bordeaux[58] and went on to help the finished the season in the 4th place at two points of a qualification in the Champions League.

[61] In a match against Lille on 29 January 2016, Nkoulou captained Marseille for the first time following Steve Mandanda's absence, which they drew 1–1.

With his contract expiring at the end of the 2015–16 season, Nkoulou attracted interests around clubs, such as Málaga,[69] Schalke 04,[70] Juventus[71] and Lazio.

It is a wink to those close to me, because I am the youngest of three children.”’’[75] Nkoulou played his first official match for Lyon at the Trophée des Champions, making his first start, in a 4–1 loss against Paris Saint–Germain.

[78] Around the same time he was competing with Mouctar Diakhaby,[79] Nkoulou's performance soon came under criticism by observers, prompting Manager Bruno Génésio defended him.

[80] On 5 August 2017, Italian club Torino announced they had signed Nkoulou on a year-long loan with an option to purchase.

[84] In August 2019, Nkoulou asked to not be selected for Torino's Serie A fixture against Sassuolo,[85] and their UEFA Europa League play-off against Wolverhampton Wanderers, with a desire to transfer to AS Roma.

[86] In September, with no transfer taking place, he wrote a letter saying he had decided to "leave the difficult moment of the summer behind me", and apologised to Torino fans, staff, and his teammates.

After spending time as a free agent, on 7 October 2021, Premier League club Watford announced the signing of Nkoulou on a deal until the end of the season.

[89] On 23 August 2022, Nkoulou joined Super League Greece club Aris on a free transfer on a two-year contract.