The Gunners currently sit top of the Premier League table after seven rounds of fixtures.
Flamini rejoined Arsenal on a free transfer in August following five years at AC Milan.
Fellow Frenchman Giroud, who has scored six goals in 11 league and cup games this season, is delighted with the contribution made by Flamini.
Speaking to L'Equipe, Giroud said: "This is perhaps the player who Arsenal have missed."
Meanwhile, Flamini has expressed his delight at returning to the Emirates Stadium, a place where he feels very much at home.
"I feel a little like I was never gone, but I'm not really surprised because I know this club by heart," he told France's largest sports newspaper.
Arsenal's season continues this afternoon when they play host to Norwich City, whom the Gunners have failed to beat twice in their last three attempts.