The Whites will play at the Kaftanzoglio Stadium in Thessaloniki on Sunday September 5, kick-off 9pm local time.
The 25,000 seater stadium has been revamped due to its inclusion as an Olympic venue for this year's games and is due to host several football group games and the semi-finals.
No fixtures are being played that weekend due to internationals with England travelling to Austria on the Saturday.
The last time Leeds played in that stadium was in 1973 when Milan won a controversial European final 1-0.
Iraklis finished eighth in the Greek top flight last season and have competed in the Uefa Cup six times.
The 25,000 seater stadium has been revamped due to its inclusion as an Olympic venue for this year's games and is due to host several football group games and the semi-finals.
No fixtures are being played that weekend due to internationals with England travelling to Austria on the Saturday.
The last time Leeds played in that stadium was in 1973 when Milan won a controversial European final 1-0.
Iraklis finished eighth in the Greek top flight last season and have competed in the Uefa Cup six times.