Mosimane joined Al Ahly just over two months ago from Mamelodi Sundowns, with whom he won the domestic treble last season of the league, the Telkom Knockout and the Nedbank Cup.
On his arrival in Cairo, Al Ahly were already well on the way to the title, which Mosimane ensured they claimed with a strong finish.
He was more severely tested in the Champions League final against bitter rivals Zamalek last Friday night, but managed to triumph 2-1 to add to his continental success with Sundowns in 2016.
Ther former Bafana Bafana head coach then guided the Red Devils to a 2-1 semi-final win over Al Ittihad Al Iskandary on Tuesday.
Meanwhile, El-Gaish had earned their spot in the final with a surprise 3-1 victory over Zamalek to make it to their first ever cup final since formation.
And after a tense, goalless first half of Saturday's match, it was the 2020 African champions who were to draw first blood when Mahmoud Kahraba gave them the lead in the 65th minute.
They were agonisingly close to victory only for Nasser Mansi to score in the second minute of added time.
While boosted by their equaliser, El-Gaish had the wind taken out their sails a short while later when Ahmed Eldin was sent off in the 96th minute.
But the gutsy cup final debutants were able to hang on with a man short right through the 30 minutes of extra time to make it through to the penalty shoot-out.
That, however, proved a hurdle to far for El-Gaish as the serial-winning Al Ahly side triumphed 3-2 on spot kicks.
Mosimane has also won a record five domestic league titles in South Africa, together with three Nedbank Cups, two Telkom Knockouts, the 2017 Caf Super Cup, and the SAA Supa8. That includes the 56-year-old’s time in charge of SuperSport United, where he won two of those domestic cups.
The former Bafana Bafana head coach has been named Coach of the Season in South Africa on five occassions.