Victor Boniface scored for the visiting team in the 51st minute at the BayArena.
Leverkusen was stunned and struggled to respond as Belgian football club Saint-Gilloise kept all its men behind the ball to maintain the narrow lead.
The host found it difficult to penetrate Saint-Gilloise’s well-organized defense and had to wait until the 83rd minute when its Iranian forward Sardar Azmoun set up Florian Wirtz who unleashed a 20-meter strike to secure a 1-1 draw in front of the home crowd.