Wenger believes that his defensive duo have shown that their understanding has reached its peak in the last two matches, keeping Dortmund and Liverpool at bay with a "huge contribution" in both games.
When asked if a spirited display in Dortmund was the pair's best together for the club, Wenger said: "Yes, it was. We have had two clean sheets now in two big games and you never do that without a huge contribution from your centre-backs.
"It's a mixture of quality but as well a calm confidence with no panic in very heated situations.
"These two are at their peak in these kinds of situations."
Koscielny and Mertesacker face another stern test of their defensive steel this weekend, when Arsenal face Manchester United at Old Trafford.