The Frenchman has revealed the defender has recovered from a head injury picked up in the first leg in Turkey while the 21-year-old was rested against Fulham
The Gunners beat the Turkish side 3-0 in Istanbul on Wednesday and look virtually assured of a place in the tournament proper, ahead of Tuesday’s second leg.
Koscielny was taken off against Fenerbahce after sustaining a head injury that saw him miss Saturday’s 3-1 win over Fulham.
However, the defender could return to the starting XI at the Emirates, alongside Wilshere who also did not feature at Craven Cottage.
"[Kosicelny] is fit [after his cut to the head] and in the squad. I've not decided if I will start him or not," Wenger told the club’s official website. "[Wilshere] will play tomorrow."
The Frenchman also revealed why he had opted to rest Wilshere on Saturday, after an impressive display against Fenerbahce.
"It is difficult because you don’t know how the body responds and when a player plays a good game he wants to continue," he explained. "We have a good communication between him and the medical department. He played 45 minutes for England after two 90-minute [games].
"He had not played 90 since February. The numbers suggested he needed a breather."
And Wenger insists he will field as strong a team as possible despite holding such a strong first-leg lead.
"It says it all [that I won't rest players]. It shows how important it is to us. It's of course a very, very, very important tie for us," he explained.
"We want to be in the group stage the next day, and that demands attitude and commitment and desire to play the game with full power, like we love to do."