Fadl, who started for the first time under Manuel Jose, ended a series of missed chances with the winning goal on 82 minutes at the Military Academy Stadium.
The victory lifts Ahli to second place temporarily, three points adrift of leaders Zamalek who will visit Petrojet on Wednesday. Gaish remain 10th.
Ahli boss Jose made some changes to the side that beat Police Union last week, handing Algerian starlet Amir Sayoud his first start this season.
Sayoud, along with Fadl and Mohamed Barakat, replaced Mohamed Abou-Treika, Osama Hosni and Dominique da Silva.
Full marks to keepers
Ahli dictated play in a one-side first half, but their first genuine attempt on goal came in the 28th minute, which witnessed a blitz of saves by Gaish keeper Mohamed Al-Shennawi.
The former Ahli youngster made three saves in one minute to deny Sayoud a debut goal from close range, seconds before foiling Barakat and Sayed Moawad.
Ahli kept the pressure on and five minutes later Fadl was sent through by a clever Barakat header, only for the lone Ahli striker to blast wide of the post.
A minute later, Fadl returned the favor to Barakat with an incisive through pass, but Al-Shennawi made another fine intervention to foil the Ahli midfielder.
The save of the first half came from the other end of the field though as Amer Sabri almost finished off a swift counter attack, only to be thwarted by an excellent save from Ahmed Adel.
Fadl faith
Jose introduced Abou-Treika for Sayed Moawad at half time, switching to 4-4-2 with central defender Ahmed Fathi moving to left back.
Fadl was Ahli’s most active player upfront but looked rusty in front of goal as he missed another fine chance to break the deadlock after the hour mark.
Jose brought on strikers Dominique and Geddo, but opted to keep the faith in the misfiring Fadl, who appeared to be receiving a speech of encouragement from his manager prior to Ahli’s final substitution.
The in-form Al-Shennawi was back again to deny the Reds on 73 minutes, this time parrying away a point-blank header by Abou-Treika.
Eight minutes from time, Jose’s decision to keep Fadl paid off as the Ahli striker was finally on target with his first goal since September.
Al-Shennawi came off his goal to thwart Dominique as Fadl chased the loose ball before slotting home in an empty net with a delicate chest touch on the second attempt.
Dominique should have doubled Ahli’s lead two minutes later, but blasted his effort over the bar after cleverly avoiding the attentions of Gaish’s last defender.
Four minutes from the end, goalkeeper Adel almost gave away the clean sheet when he failed to catch an innocuous freekick, but was saved by an excellent clearance from Ahmed Al-Sayed.