He began his football career in the youth system of Football Club Brussels before moving to England to join Birmingham City. He turned professional with Birmingham, but never made a first-team appearance, and returned to Belgium to join Mons in January 2013. A midfielder, he has represented Belgium in international football at levels up to under-21.
He played football for Ritterklub vsv Jette before joining the youth system at Football Club Brussels.
As a 16-year-old, he moved to England to start a two-year scholarship programme in Birmingham City"s Youth Academy in 2009. He played in the under-18 and reserve teams, and was rewarded with a two-year professional contract in July 2011.
Academy manager Kristjaan Speakman described him as a central midfielder who "can play in either a two or a three and I think he"s most suited to playing deep. He"s got some real assets in terms of his physical presence and his ability to get round the pitch, but is also neat and tidy on the ball." The Birmingham Mail"s correspondent assessed him as "a powerful player with endurance is good in the air". but was not included in the matchday squad.
Following injuries to central midfielders Guirane North"Daw, Keith Fahey and Jordon Mutch, Ntambwe was included in the travelling party for the visit to Ipswich Town in the Football League Championship on 17 April, but again failed to make the matchday squad.
Although numerous youngsters were given first-team squad numbers in the 2012-2013 season, Ntambwe was not. He returned to Belgium in January 2013 to join Pro League club Mons. He signed an 18-month contract with the option of a further year.
After playing 90 minutes for the club"s under-21 side in midweek, Ntambwe was included in Enzo Scifo"s starting eleven to strengthen the midfield for the visit to Standard Liège on 10 February.
Ntambwe was sent off after 73 minutes of his third match, against Kortrijk, for a reckless tackle, having already been yellow-carded earlier in the game. Scifo attributed it to youthful enthusiasm which he needed to learn to control.
Ntambwe represented Belgium at all levels from under-15 to under-20. He captained and played regularly for the Belgium under-17 team in the 2009-2010 season.
Ntambwe received his first call-up to the under-21 team for the 2015 European Championship qualifier against Cyprus in March 2013.
He played three times for the under-21s in the 2013 Toulon Tournament, before making his competitive debut as a second-half substitute as Belgium beat Italy 3–1 in their first qualifying match for the 2015 European championships.
He made his under-19 debut in the starting eleven for a friendly against Serbia under-19 in February 2012, and later that year, he was a member of the under-20 team that played England C in the International Challenge Trophy.