Ozil has endured a mixed campaign at the Emirates Stadium since joining the club from Real Madrid for £42m in the summer, but Lehmann has insisted that supporters won't see the best of the German international until he has gotten used to the "rhythm" of the Premier League.
The 44-year-old told talkSPORT: "Mesut Ozil will be a big success at Arsenal.
"You have to remember that every player who has come from abroad needs to get used to the rhythm of the Premier League.
"You don't know how your body is going to react after the winter period - in no other league is it so hard to play throughout the whole season. You get a little break in Spain and Germany. It is his first season at Arsenal, but he is a fantastic player."
Ozil has scored six times in 34 appearances for Arsenal this season.