Wenger was pleased with the Cameroon midfielder's contribution for the first goal.
"For the first goal Song did something exceptional for a defensive midfielder," Wenger said.
"I am pleased for him because we had quite a difficult start in midfield in the first half, but we took over in the second half.
"Overall it was a good game. Dortmund are a good team. They started stronger than us but we were patient and intelligent."