Siebatcheu is a youth exponent from Stade de Reims having joined the club as a 7-year-old. He made his Ligue 1 debut on 31 January 2015 against Toulouse replacing Alexi Peuget after 67 minutes in a 1–0 away defeat. On 9 August 2015, Siebatcheu scored his first Ligue 1 goal in only his second appearance, against Girondins de Bordeaux. He signed his first professional contract in September 2015 committing to a three-year deal with Reims. On 24 October 2017, Siebatcheu was named the Ligue 2Player of the Month for September, due to ranking among the league's best in both goals and assists, while leading Reims to the top of the Ligue 2 table. On 16 December 2017, he set a career high for goals in a match by netting a hat trick against Valenciennes. Siebatcheu helped Stade de Reims win the 2017–18 Ligue 2 season and promotion to Ligue 1 for the 2018–19 season while also setting a record for the number of points in a Ligue 2 season. He finished the season with 17 goals, the second-highest total among all Ligue 2 players, as well as 7 assists.
Rennes
On 12 June 2018, Siebatcheu signed a contract with Ligue 1 side Rennes. On 20 September, he made his European debut in the 2018–19 UEFA Europa League group stage for Rennes and drew the game-winning penalty kick against FK Jablonec. On 8 November, he scored his first European goal, against Dynamo Kyiv. On 22 December, he had his first Ligue 1 brace, scoring two goals and adding an assist against Nîmes Olympique in a 4–0 victory.
International career
On 25 July 2015, Siebatcheu revealed in an interview that he was born in Washington, D.C. and still holds an American passport. He is eligible to play for France, Cameroon, or the United States internationally. Siebatcheu was called up for the first time to the France national under-21 football team for two friendly matches in June 2017. He scored against Albania under-21s in his debut, and also played against Cameroon under-20s. However, he has not been recalled to France at any level since then. On 17 May 2018, it was reported that the United States Soccer Federation had inquired about Siebatcheu. He was called up by the USMNT for a match against France in June 2018, but declined the call-up, citing his transfer from Reims to Rennes, while leaving the door open for possible inclusion in the United States squad in the future.
