The French forward earned praise for his goal in the 3-1 victory over West Ham United on Tuesday, and Wenger believes that it was a clear sign that he is beginning to feel confident again.
"The quality of the goal gives him, I think, confidence again, gives him credibility again for people who questioned his ability, so that is important," the Gunners boss told reporters.
"He is a strong lad, strong mentality, strong positive guy. He has a great mentality that's what I think got him back.
"He has scored 20 goals that is a great record and he is working very hard for the team."
Giroud is expected to start in attack against Hull City on Sunday.