The central defender has penned a four-year deal with the Red Devils, the club said on their official website.
Zamalek looked close to signing Abdul-Fadil after having an EGP7-million bid for him accepted by Ismaili.
However, the White Knights were unable to meet his contract demands and the deal eventually collapsed.
Ismaili's fierce rivals Ahli were waiting in the wings to acquire Abdul-Fadil's services.
"Ahli increased their offer to EGP7.5 million and agreed to sell right-back Ahmed Sedik to us as part of the deal," Ismaili chairman Nasr Aboul-Hassan told FilGoal.com.
"We had to accept Ahli's offer because, unlike Zamalek, they will pay the transfer fees in cash. Ismaili are pushed for money."
Although Ahli's current squad boasts several ex-Ismaili players, none of them joined Ahli directly from the Dervishes.
Abdul-Fadil has become the second player Ismaili sell to Ahli in a decade after midfielder Mohamed Abdullah, who joined the six-time African champions in 2005.
The heated rivalry between both sides makes it difficult for them to swap players.
Abdul-Fadil's arrival will boost Ahli manager Hossam Al-Badri, who has seen his side suffer from defensive problems during their pre-season friendlies.
The 26-year-old, who can also play as a right back, is likely to partner Egyptian international Wael Gomaa in the heart of Ahli's defense.
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كأس عاصمة مصر - موعد مباراة الزمالك المقبلة ضد زد والقناة الناقلة
معتمد جمال يمنح لاعبي الزمالك راحة لمدة 4 أيام
بعد إعلان القائمة.. رباعي يبحث عن الظهور الأول بقميص منتخب مصر
مروان عطية يغيب عن مباراة أنجولا بتصفيات أمم إفريقيا
قائمة منتخب مصر - انضمام علي محمود لأول مرة.. والبلعوطي يعوض غياب الشناوي
خالد جلال: إذا كانت النتيجة منصفة سنسجل 3 أهداف ضد الزمالك.. ومندهش من الإصابات
مؤتمر معتمد جمال: لم أكن أعلم طريقة لعب غزل المحلة.. ولهذا السبب قمت بتأخير التبديلات
بنتايك: لا يوجد لقاء سهل في الدوري.. وزملائي سبب حصولي على جائزة رجل المباراة












كأس الرابطة - برايتون يقصي مانشستر يونايتد.. وتأهل فيلا وإيفرتون