With Esteghlal leading 1-0 at a packed Azadi Stadium, Persepolis were staring defeat in the face.
Arash Borhani put the Blues ahead just after the break, taking advantage of a defensive lapse to put Esteghlal 1-0 ahead.
Both teams had chances to add to the scoreline.
Alireza Nikbakht-Vahedi hit an Esteghlal post, Karimi missed a gilt-edged chance and Borhani should have scored at least one more.
With time almost over, Karimi sent the Red fans wild with delight with his equalizer and denied the Blues a famous win.
Persepolis are in fourth while Esteghlal are in seventh though the season is still young.
Zob Ahan are in second after a 6-3 thrashing of a struggling Saipa side.
Sepahan won 1-0 at Rah Ahan while Pas and Malavan drew 0-0.
Leaders Bargh won the previous day.
1: Bargh 17 2: Zob-Ahan 17 3: Peykan 15 4: Persepolis 15 5: Mes 15