The French striker, who was signed from Montpellier for around £10m last summer, was criticised after missing a number of chances during Tuesday's goalless draw with Everton in the Premier League.
"He gives a lot and I think for a first season he's doing extremely well," Wenger told reporters. "He has a fantastic attitude and a positive mentality. He has given us another dimension."
Giroud has scored 17 goals in all competitions for Arsenal this season.