Wenger will lead Arsenal for the 1,000th time when they take on city rivals Chelsea in the Premier League on Saturday.
The French manager first joined Arsenal in 1996 and, although his tenure has become characterised by a dearth of silverware over the past few years, Flamini remains convinced Wenger has been brilliant for the Emirates Stadium outfit.
"It's an unbelievable achievement. He (Wenger) means so much to the club for the achievements he has done until now. Congratulations to him, first of all," the French midfielder said on Wednesday.
"I think it's someone who knows exactly what he wants. He has a vision since the beginning, he's moved to Arsenal and he still has the same one. He knows exactly how he wants to play. That's remarkable.
"He's not really changed, he's still the same person. He had a philosophy before and he still has the same ones, that's why it's so easy for me to come back and to find my place in this team."
Flamini was part of the Arsenal team to last win a trophy - the 2005 FA Cup - before returning to the club this campaign after five seasons with Milan in Italy.
The 30-year-old would love to see the current Arsenal side reward Wenger's loyalty to the north London club by breaking the trophy drought this season.
Arsenal (62 points) trail Premier League leaders Chelsea by four points heading into Saturday's clash and have a game in hand, while Liverpool sit second, ahead of Wenger's team on goal difference.
Manchester City also remain in the hunt for the title in fourth with 60 points and having played two less games than Arsenal and Liverpool.
"We have a few more games to come, which are not easy, because Chelsea and Manchester City are also fighting for the title," Flamini said.
"In the title race, it's very important not to drop any more points because it's not a marathon now, it's a sprint. We have a few more games and we want to win every single one.
"The Premier League is one of the objectives but we still have the FA Cup and we really want to make something of this competition too.
"It's a great opportunity, everyone is waiting for Arsenal to win a title and everyone is talking around the club that Arsenal haven't won a title for a while. It's a great opportunity for us and it's in our hands and I can assure everyone we will do everything to go through and win it this year."
