Ndombele was born in France to parents from D.R. Congo. As a child, he played at FC Épinay Athlético, a club based in Épinay-sous-Sénart, about 20 kilometres south-east of Paris, in Essone. He then moved to Brittany when he was just 14, in order to play for Guingamp, where he spent three seasons. He wasn't offered a professional contract at the end of his development. At only 16, he made his senior debut, on 11 January 2014 with the reserves, by replacing Vital N'Simba near the final whistle. He then signed for SC Amiens, who'd just been relegated from French Ligue 2 in June 2014, he took this as an opportunity to trial at numerous clubs but wasn't signed. The issue was that N'dombele was criticised for being "overweight", this was the main reason that he wasn't signed by clubs, even though trialists were aware that he was a good playmaker. Ndombele played 2 seasons in Championnat National 3 with the Amiensreserve team. He only played one game during the 2014–15 season, 8 November 2014, once again, coming on late in the match. He became a regular during the 2015–16 season, taking part in 18 matches. He started for the first time on 5 September 2015 at the age of 18 years and 9 months.
On 31 August 2017, Ndombele moved to Lyon on a one-year loan. According to L'Équipe, Lyon paid €2 million for the loan. Lyon also secured an option to sign him permanently for €8 million, plus a possible €250,000 in bonuses and 20% of any profit made should he be transferred from Lyon to another club. Ndombele made his competitive debut for Lyon's first team in the 2–0 Ligue 1 away loss to Paris Saint-Germain on 17 September 2017; he started the match and was replaced by Christopher Martins in the 72nd minute. On 15 February 2018, Ndombele scored a goal in the 46th minute of their 3–1 home win over Villarreal CF in the round of 32 first leg of the 2017–18 UEFA Europa League. His first season at Lyon was very successful as he provided great energy to the team while helping them get back to Champions League football for the next season as Lyon finished third behind PSG and Monaco. He became an indisputable starter for the team and was, alongside Ferland Mendy and Houssem Aouar, one of the great young players of his team. Few teams also showed interest for the French prodigy but Lyon made it clear that he won't be sold and won't return to his former club Amiens as Lyon paid the €8 million release clause to buy him. The next season, Lyon signed him permanently as it was previously stated in the loan deal and his contract was extended until 2022 with the Gones. He started off the season well and for his first match in the UEFA Champions League against Manchester City at the Etihad Stadium, he played brilliantly against world-class players while helping his team upset the English giants. This 5-star performance helped him gain a lot of attention from big European teams such as Manchester City, PSG and even Real Madrid. He then scored his first Champions League goal against TSG 1899 Hoffenheim on 11 November 2018. As the season progressed, he played consistently and it appeared inevitable that he was going to leave that summer. He scored his first Ligue 1 goal against Nîmes on 24 May 2019 and Lyon eventually finished 3rd in Ligue 1, behind Lille and PSG. His team was also eliminated by FC Barcelona in Champions League Round-of-16 and finished the season trophyless despite giving out great performances against superior teams. Lyon's president Jean-Michel Aulas announced that he had received offers for Ndombele and that he might leave that summer.
Tottenham Hotspur
On 2 July 2019, Ndombele signed for Tottenham Hotspur in a deal worth €62 million plus up to €10 million in add-ons. Ndombele made his debut in the 2019 International Champions Cup against Juventus. Within a minute of being substituted on and with his first touch in a Tottenham shirt, Ndombele assisted Lucas Moura. Tottenham won the game 3–2. On 10 August 2019, Ndombele made his Premier League debut for Tottenham and scored the first league goal for the club in the 2019–20 season, helping the team to come from behind to win 3–1 against Aston Villa. Due to his poor form, after a 1–1 draw with Burnley FC on 7 March 2020 Tottenham manager José Mourinho criticised Ndombele's performance and his perceived unprofessionalism saying "He's a player with great talent. He has to know he has to do much better and know I cannot keep giving him opportunities to play because the team is much more important."..
