Midfielder Ghasem Hadadifar hit a 57th-minute winner from a free kick at Foolad Shahr Stadium.

Hilal missed a golden opportunity four minutes before halftime when midfielder Christian Wilhelmsson missed a penalty kick.

Zob Ahan will travel to Riyadh for the second leg on Oct. 20, with the winner to play against either Saudi's Al Shabab or South Korea's Seongnam Ilhwa in the one-leg final on Nov. 13 in Tokyo. Shabab won its first leg 4-3 on Tuesday.

Zob Ahan was under pressure to win at home against Hilal, which hasn't won away all season. But  Hilal hasn't lost at home for seven years in the Asian Champions League.