The Frenchman has impressed since rejoining the club during the summer transfer window, when he was a free agent having been released by AC Milan.
The tenacity of 29-year-old Flamini - who left the Emirates Stadium in July 2008 when he ran down his contract - has been a real plus for Wenger, allowing the likes of club-record £43million signing Mesut Ozil and Wales international Aaron Ramsey greater freedom.
"Flamini has given us a balance between attacking and defending. He is someone who accepts the dark role in the team," said Wenger, whose side will be looking to consolidate their place at the top of the Barclays Premier League with victory at West Brom on Sunday.
"Sometimes before in big games we looked frail defensively, and he gives us more in that sense.
"I don't know if he will turn out to be one of the most important signings I have ever made, but I think it was an important signing."
Wenger revealed how he almost did not sign up Flamini once again after the player returned to his old club to work on his fitness.
"I had hesitations about it, I must tell you. He left us and players who leave do not necessarily come back," the Arsenal manager added.
"But what is most important is what is right for the club. When I saw him in training I saw he could give us something the team needs.
"He is 29 now and you know better at that age who you are as a player.
"When he first arrived here he wanted to play in a more offensive role, but today he knows his qualities and accepts them.
"His attitude to join us convinced me because he had other proposals as well.
"Once he decided to wait on us to see if he could sign here, you think there is something special."
Wenger had looked to bring in a striker over the summer but saw bids for both Gonzalo Higuain and Luis Suarez fail to materialise.
Despite France international Olivier Giroud spearheading the attack on his own in front of a dynamic midfield, Wenger is convinced enough forward cover is in place.
"(Nicklas) Bendtner is ready to play, Yaya Sanogo is not ready. We have decided to work with him until Christmas and after that he should be ready as well," Wenger said.
Arsenal travel to West Brom - where a young team won through on a penalty shoot-out in their Capital One Cup tie last week - out to record what would be a remarkable 11th straight victory in all competitions.
However, any talk of whether this current group could prove as good as his last championship-winning side of 2003/04 was quickly played down.
Wenger said: "It is too early to compare because the Invincible side did not lose for 49 games. We have quality though."