Mane netted from long-range with 12 minutes of the contest remaining, a result that leaves former Liverpool teammate Mohamed Salah still searching for his maiden continental trophy.
The first half, like most of the contest, was a rather cagey affair as Senegal had most of the ball but could not break down a solid Egyptian defence.
Nicolas Jackson had the first real opportunity but fired over the bar while Pape Gueye eventually tested Pharaohs goalkeeper Mohamed El Shenawy.
The talking point in the opening stanza came five minutes before the halftime break when both benches clashed after Senegal head coach Pape Thiaw strayed into Egypt's technical area to issue instructions.
Senegal again saw more of the ball after the interval with Lamine Camara and Iliman Ndiaye attempting long-range efforts.
Mane eventually broke the deadlock in the 78th minute when he picked up the ball just outside the box and fired a low effort past El Shenawy.
Egypt coach Hossam Hassan looked to his bench for a way back into the contest and threw on Zizo, Mostafa Mohamed and Salah Mohsen.
Senegal shot-stopper Edouard Mendy denied Manchester City forward Omar Marmoush late on as the Lions of Teranga progressed into the final.
Senegal will be without captain, and key defender, Kalidou Koulibaly and midfielder Habib Diarra for the showpiece game due to suspension as they await Nigeria or hosts Morocco on Sunday.