The Emirati side grabbed a crucial away goal just before the hour-mark to level the scores in Muscat and enhance their chances of reaching the final ahead of the home leg next week.
After a nervy start to the first leg, it was the visitors who threatened first as Brett Holman and Ibrahima Toure wasted chances to open the scoring.
It was Al Nahda who broke the deadlock in the 39th minute, though, when Anwar Al-Hinai found the back of the net.
They were able to hold onto that lead until the break, but the visitors were level within 15 minutes of the restart.
Leonadro Lima was the man to peg back Al Nahda from the penalty spot after Habib Al Fardan had been upended in the area.
Al Nasr nearly snatched victory in the closing minutes as Toure wasted a late headed opportunity, and it will be all to play for in the second leg next Wednesday.
