The 27-year-old was handed his fifth appearance in the European competition at Vasil Levski and delivered an impressive showing.
The Cameroon international scored his fourth goal in the tournament which moved Gerardo Seoane’s men closer to the knock-out stage.
The game started with both sides trying to open the scoring but missed several chances in the opening 30 minutes.
Nsame, however, broke the deadlock for the Swiss side in the 34th minute which made the difference in the encounter.
The centre-forward fired his effort past the reach of goalkeeper Gustavo Busatto after receiving a timely pass from Silvan Hefti.
Despite several attempts to level proceedings by CSKA Sofia, Young Boys held their nerve to secure all three points in the match.
Nsame featured for the duration of the game and Guinea international Jules Keita was introduced moments before the full-time whistle.
With the win, Youn Boys are second on the Europa League Group A table after gathering seven points from four matches.
The Cameroon international has now scored nine goals across all competitions and provided five assists in 15 appearances.
Nsame will hope to continue his impressive performances when his side takes on AS Roma in their next outing in the European competition on December 3.
Before that, Young Boys will square off against Lausanne Sport in a Swiss Super League game on November 29.
Nsame has two caps for the Cameroon national team and his current form could see him make a return to the West African side, having last featured for them in June 2019.