Zobahan were punished for a below-par display in the 71st minute when Amin embarked on a strong run from inside his own half and found the back of the net from outside the box.
It was the Iranian club’s first defeat in the competition and sets up a potentially tense final clash with Al Ittihad on Match Day Six.
Despite missing Ismail Matar, Pinga and Magrao, Al Wahda looked the better side in the first-half, creating and wasting almost half a dozen chances while Zobahan hardly had a sight of the hosts’ goal.
Hassan Amin’s cross in the fifth minute was headed the wrong side of the far post by Saeed Al Kathri, who went on to squander further openings.
In the starting line-up as Matar’s replacement, Al Kathri was off target in the 11th minute when he first hit a defender from close range and then ballooned the rebound wide.
Five minutes later, he wasted another opportunity after Fernando Baiano had set-up him up with a neat pass.
Zobahan were struggling to string together a decent passage of play and in the 21st minute they had another escape when Mohammad Al Shehhi’s low shot flew wide the left post.
The visiting team suffered a blow when goalkeeper Gordan Shahabaldin limped off in the 26th minute to be replaced by Abbas Ghasem. One minute later Zobahan had their first effort on goal with Ismael Farhadi getting his head to a Hasan Ashjari free-kick but keeper Adel Al Hosani gathered safely.
Zobahan did, however, have the best chance of the first period in the 42nd minute when impressive left-back Ahmadi Mohammadali delivered a dangerous low cross but Mohammad Mansouri fired wide from close range
Mansouri tried to make amends with a powerful drive three minutes into the second-half but Al Hosani was on hand to thwart the danger.
Gaining some momentum, Zobahan again came close in the 56th minute but a powerful drive by Ghassem Hadadifar was met with a diving save from Al Hosani.
Ghazi Najafabadi continued Zobahan’s poor finishing when he failed to reach a cross from the right, while at the other end Amin’s shot through a crowded box hit the inside of the left post in the 67th minute.
But four minutes later, Amin drove forward from his own half and fired home from well outside the box, giving Ghasemi no chance as Al Wahda punished the group leaders for their first-half profligacy.
The goal failed to elicit any response from the visitors and Al Wahda twice came close to a second as Haider Alo Ali’s drive hit the post and Abdul Rahim Juma’s booming drive also smacked the right upright as the UAE side proved well worth their win.