The win means that Leverkusen are now six points clear of Jurgen Klopp's side and have closed the gap on leaders Bayern Munich to four points.
"I am especially pleased for the team," Hyypia told reporters.
"In the first-half, we really showed what's possible. After the break, we fought hard and we won.
"The victory was important because Dortmund were only three points behind us."
Leverkusen's next game sees them travel to Real Sociedad in the final Champions League Group A game, with the German team currently sitting in third place.