Flamini quit the Gunners after his best season for the club, choosing to join AC Milan rather than sign a new contract at the Emirates.
And Wenger has admitted the incident weighed on his mind when deciding whether or not to bring the 29-year-old back to North London.
“First of all I believe that he realised what he had here,” Wenger told the Arsenal official website.
“When you’re very young, it is difficult to understand what he had at Arsenal.
“I must say I was reluctant to sign him again, but he was so honest in his statement that he wants to play the kind of football we play, that he wants to help us to win. He convinced me through his attitude and his desire in training that he will be the right signing for us.
“It was his attitude. He could have gone somewhere else. He had offers but he wanted to put it right with this club and I think he felt somewhere that he had something to bring to the piece here. He was determined to do that.”
Flamini has performed as though he has never been away in the two appearances since his return, and Wenger is confident the Frenchman can help the Gunners end their trophy drought.
“Flamini is absolutely crucial to the balance of the team,” he added.
“He had not played since May and when you see how well he came in, it shows you how focused and how dedicated he was in his preparation.”
[cat_link cat=”arsenal” type=”grid”]